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Basis of Presentation and Significant Accounting Policies (Detail) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Jan. 01, 2017
Accounting Policies [Abstract]      
Effective income tax rate, continuing operations 12.90% 33.80%  
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount   $ 1.5  
Restatement adjustment [Member] | Accounting Standards Update 2016-18 [Member]      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Increase in restricted cash   $ 444.4  
Retained earnings [Member] | New accounting pronouncement, early adoption, effect [Member] | Accounting Standards Update 2016-09 [Member]      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Cumulative effect adjustment     $ 1.1