Quarterly report pursuant to Section 13 or 15(d)

Shareholders' Deficit - Additional Information (Detail)

v3.10.0.1
Shareholders' Deficit - Additional Information (Detail)
$ / shares in Units, $ in Millions
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Apr. 24, 2018
May 31, 2018
USD ($)
$ / shares
shares
Feb. 28, 2014
USD ($)
$ / shares
shares
Sep. 30, 2018
USD ($)
$ / shares
shares
Jun. 30, 2018
shares
Mar. 31, 2018
USD ($)
$ / shares
shares
Sep. 30, 2017
USD ($)
$ / shares
shares
Jun. 30, 2017
USD ($)
$ / shares
shares
Mar. 31, 2017
USD ($)
$ / shares
shares
Mar. 31, 2014
USD ($)
Sep. 30, 2018
USD ($)
$ / shares
shares
Sep. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
Feb. 21, 2017
USD ($)
Stockholders Equity [Line Items]                              
Share repurchase program authorized amount       $ 1,500.0             $ 1,500.0       $ 1,500.0
Share repurchase program, remaining authorized capacity       113.3             $ 113.3     $ 233.0  
Share repurchase program expiration date                     Feb. 21, 2020     Jun. 30, 2017  
Accumulated deficit       $ (575.2)             $ (575.2)   $ (248.1)    
Repurchase of common stock, value                     $ 736.4 $ 346.2      
Treasury stock shares, at cost | shares       10,000,000             10,000,000   10,000,000    
Shares repurchases, value                     $ 600.7 299.2 $ 4.2    
Withheld for tax purpose for share-based compensation plans                     135.7 47.0      
Payments for share repurchases                     740.6 346.2      
Stock split conversion ratio 2   2                        
Increase (decrease) in additional paid-in capital, other                     (4.9)        
Terminating result of portion of capped call transactions cash received                     55.9        
Other comprehensive income (loss) before foreign currency translation adjustments reclassifications, Tax expense (benefit)       $ (2.4)     $ 1.8       (4.4) 3.5      
Convertible Senior Notes Due 2019 [Member]                              
Stockholders Equity [Line Items]                              
Stock split conversion ratio     2                        
Capped call transactions [Member]                              
Stockholders Equity [Line Items]                              
Capped call transactions with financial institutions     $ 123.8                        
Capped call transactions price per common share | $ / shares     $ 60.39                        
Increase (decrease) in additional paid-in capital, other                   $ (123.8)          
Terminating result of portion of capped call transactions cash received                     $ 55.9        
Capped call transactions [Member] | Common Share [Member]                              
Stockholders Equity [Line Items]                              
Weighted-average adjusted cap price per common share | $ / shares       54.38             54.38        
Capped call transactions [Member] | Convertible Senior Notes Due 2019 [Member]                              
Stockholders Equity [Line Items]                              
Convertible notes conversion price | $ / shares     $ 43.14                        
Prepaid forward share repurchase transactions [Member]                              
Stockholders Equity [Line Items]                              
Forward share repurchase transactions amount     $ 685.8             685.8          
Forward transactions, shares to be purchased | shares     19,900,000                        
Average cost per share of shares repurchased | $ / shares     $ 34.51                        
Settlement date of forward transactions                     Aug. 15, 2019        
Forward counterparties shares purchased and subsequently retired | shares       2,000,000             10,400,000        
Non-cash interest expense relating to unamortized non-cash issuance costs       $ 0.6             $ 3.7        
Shares outstanding under forward purchasing transactions | shares       9,500,000             9,500,000        
Accumulated deficit                   (653.9)          
Additional paid-in-capital                   (31.9)          
Non-cash forward transaction issuance costs                   $ 35.8          
Non-cash interest expense relating to amortization of non-cash issuance costs       $ 1.5     $ 1.6       $ 7.8 $ 4.8      
Open market purchases [Member] | Indirect wholly owned subsidiary [Member]                              
Stockholders Equity [Line Items]                              
Average cost per share of shares repurchased | $ / shares           $ 33.90 $ 36.19 $ 33.53 $ 28.05            
Repurchase of common stock, shares | shares       0 0 8,400 1,600,000 5,300,000 2,200,000            
Repurchase of common stock, value           $ 0.3 $ 58.7 $ 179.8 $ 60.7            
May 2018 Dutch Auction Tender Offer [Member]                              
Stockholders Equity [Line Items]                              
Average cost per share of shares repurchased | $ / shares   $ 52.50                          
Repurchase of common stock, shares | shares   11,400,000                          
Repurchase of common stock, value   $ 600.0                          
October 2017 Dutch Auction Tender Offer [Member]                              
Stockholders Equity [Line Items]                              
Forward share repurchase transactions amount                     $ 1.6        
Contingent value right agreement term                     2 years        
Non-transferable contractual contingent value right agreement initial fair value                         7.3    
CVR expiration period                     2019-08        
Gain (loss) recognized in other expense       $ 4.6             $ (11.4)        
Non-transferable contractual contingent value right agreement change in fair value       $ 18.3             $ 18.3   $ 6.9