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Debt - 6.875% Senior Unsecured Notes Due 2021 - Additional Information (Detail) - 6.875% Senior Unsecured Notes Due 2021 [Member] - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Jul. 22, 2016
Sep. 30, 2016
Dec. 31, 2016
Dec. 31, 2015
Apr. 26, 2011
Debt Instrument [Line Items]          
Debt instrument face amount         $ 450.0
Senior unsecured notes, interest rate     6.875% 6.875% 6.875%
Senior notes frequency of periodic payment     Interest on the notes was payable semi-annually on May 1 and November 1 of each year.    
Notes redeemed $ 450.0        
Debt refinancing charge   $ 22.5      
Redemption premium   $ 15.5