Derivatives - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2014 Interest rate swaps [Member] Agreement	Sep. 30, 2014 Interest Rate Swap Eleven [Member]	Sep. 30, 2014 Interest Rate Swap Twelve [Member]	Sep. 30, 2014 Settled Interest Rate Swaps [Member]
Derivative Instruments [Line Items]
Estimate increase to interest expense	$ 3.6
Number of derivative, interest rate swap agreement			12
Derivative, Weighted average interest rate			1.67%
Derivative, notional amount			327.9
Loss on Cash Flow Hedge Ineffectiveness	0.1	1.2
Derivative Liability, Notional Amount, Ineffective				40.0
Maturity Date					Jan. 02, 2019
Net loss					2.7
Amortized period						10 years
Fair value of derivatives in a net liability position	(1.1)
Termination value	$ (1.4)