Financial Instruments - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) Derivative	Dec. 31, 2014 USD ($) Derivative
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Carrying amount of notes	$ 358.1	$ 358.2
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	(2.7)
Designated As Hedging Instrument
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Aggregate notional amount	$ 78.9	$ 530.0
Interest Rate Swap [Member]
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative maturity date	Sep. 01, 2017
Derivative fixed interest rate	2.80%
Interest Rate Swap [Member] | Designated As Hedging Instrument
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Number of interest rate derivatives held | Derivative	1	9
Fair Value, Measurements, Recurring [Member]
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair value of swap liability	$ 3.3
Fair value of swap, net liability	3.3	$ 4.3
Level 3 [Member]
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Approximate fair value of notes	361.3	362.2
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair value of swap, net liability	$ 0.0	$ 0.0