Derivatives - Schedule of Gains (Losses) for Derivatives Designated as Fair Value Hedges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments Gain Loss [Line Items]
(Gain) loss recognized as ineffectiveness	$ (0.4)	$ (0.4)
Interest Rate Swap | Investment and other expense-net | Designated Fair Value Hedges
Derivative Instruments Gain Loss [Line Items]
(Gain) loss recognized as ineffectiveness	0.4	(1.7)
Hedged Items | Investment and other expense-net | Designated Fair Value Hedges
Derivative Instruments Gain Loss [Line Items]
(Gain) loss recognized as ineffectiveness	$ (0.8)	$ 1.3