Annual report pursuant to Section 13 and 15(d)

Shareholders' Deficit - Additional Information (Detail)

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Shareholders' Deficit - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2019
Oct. 30, 2018
May 31, 2018
Oct. 31, 2017
Feb. 28, 2014
Mar. 31, 2014
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Stockholders Equity [Line Items]                  
Common shares, shares outstanding 137,400,000           137,400,000 142,800,000 164,700,000
Preference shares authorized 7,500,000           7,500,000    
Preference shares par value $ 0.002           $ 0.002    
Share repurchase program authorized amount $ 1,500.0 $ 1,500.0         $ 1,500.0    
Share repurchase program, remaining authorized capacity 1,500.0 $ 113.3         $ 1,500.0    
Share repurchase program expiration date   Feb. 21, 2020         Oct. 30, 2023    
Forward counterparties shares purchased and subsequently retired             6,000,000.0 13,900,000  
Accumulated deficit $ (215.3)           $ (215.3) $ (526.3)  
Repurchase of common stock, shares             400,000 14,300,000 25,400,000
Treasury stock shares, at cost 10,000,000.0           10,000,000.0 10,000,000.0  
Shares repurchases, inclusive of transaction costs and issuance of CVR value             $ 0.0 $ 600.7 $ 795.3
Withheld for tax purpose for share-based compensation plans             16.7 145.4 60.4
Shares repurchases, value             16.7 746.1 855.7
Payments for share repurchases             16.7 750.3 844.2
Payments for share repurchases from prior period liability               4.2  
Share repurchases for which subsequent payment to be made               4.2  
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)             0.1 $ (2.7) 5.7
Capped call transactions [Member]                  
Stockholders Equity [Line Items]                  
Capped call transactions with financial institutions         $ 123.8        
Capped call transactions price per common share         $ 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] | Convertible Senior Notes Due 2019 [Member]                  
Stockholders Equity [Line Items]                  
Convertible notes conversion price         $ 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         19,900,000        
Average cost per share of shares repurchased         $ 34.51        
Settlement date of forward transactions             Aug. 15, 2019    
Forward counterparties shares purchased and subsequently retired 19,900,000           13,900,000 6,000,000.0  
Shares outstanding under forward purchasing transactions 0           0    
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             $ 1.2 $ 9.2 $ 6.5
Open market purchases [Member]                  
Stockholders Equity [Line Items]                  
Repurchase of common stock, shares             0    
Open market purchases [Member] | Indirect wholly owned subsidiary [Member]                  
Stockholders Equity [Line Items]                  
Average cost per share of shares repurchased               $ 33.90 $ 32.81
Repurchase of common stock, shares               8,400 10,000,000.0
Repurchase of common stock, value               $ 0.3 $ 328.6
May 2018 Dutch Auction Tender Offer [Member]                  
Stockholders Equity [Line Items]                  
Average cost per share of shares repurchased     $ 52.50            
Repurchase of common stock, 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    
Average cost per share of shares repurchased       $ 34.00          
Repurchase of common stock, shares       13,500,000          
Repurchase of common stock, value       $ 457.8          
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             $ 15.7 $ (8.8) $ 0.4
Dutch Auction Tender Offer [Member]                  
Stockholders Equity [Line Items]                  
Average cost per share of shares repurchased               $ 52.49 $ 33.49
Repurchase of common stock, shares               11,400,000 23,500,000
Repurchase of common stock, value               $ 600.3 $ 786.4