Leases - Summary of Lease Cost Recognized Over the Lease Term (Detail) $ in Millions  | 
3 Months Ended | |||||
|---|---|---|---|---|---|---|
| 
 Mar. 31, 2019  
USD ($) 
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| Leases [Abstract] | ||||||
| Operating lease cost | $ 15.8 | [1],[2] | ||||
| Finance lease cost | ||||||
| Amortization of right-of-use assets | 0.1 | |||||
| Net lease cost | $ 15.9 | |||||
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- References No definition available. 
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- Definition Amount of amortization expense attributable to right-of-use asset from finance lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
- Definition Amount of lease cost recognized by lessee for lease contract. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
- References No definition available. 
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| X | ||||||||||
- Definition Amount of operating lease expense. Excludes sublease income. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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