Derivatives - Fair Value of Derivative Instruments (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015		Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Fair Value at period end	[1]	$ 6.0		$ 2.4
Interest Rate Swap One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		25.0
Fair Value at period end	[1]	$ 0.1		0.2
Interest Rate		1.10%
Maturity Date		Jul. 31, 2016
Interest Rate Swaps Two [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 28.1
Fair Value at period end	[1]	$ 0.3		0.4
Interest Rate		1.38%
Maturity Date		Jan. 02, 2017
Interest Rate Swaps Three [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 33.2
Fair Value at period end	[1]	$ 0.2		0.1
Interest Rate		3.72%
Maturity Date		Dec. 01, 2017
Interest Rate Swaps Four [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 7.6
Fair Value at period end	[1]	$ 0.0		0.0
Interest Rate		1.00%
Maturity Date		Jan. 01, 2018
Interest Rate Swaps Five [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 55.0
Fair Value at period end		$ 0.5	[1]	0.0
Interest Rate		1.12%
Maturity Date		Jan. 01, 2018
Interest Rate Swaps Six [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 48.0
Fair Value at period end		$ 0.4	[1]	0.0
Interest Rate		1.12%
Maturity Date		Jan. 01, 2018
Interest Rate Swap Seven [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 30.0
Fair Value at period end	[1]	$ 0.8		0.4
Interest Rate		1.7775%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Eight [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.6		0.3
Interest Rate		1.7775%
Maturity Date		Jan. 02, 2019
Interest Rate Swaps Nine [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.6		0.3
Interest Rate		1.78%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Ten [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.6		0.3
Interest Rate		1.79%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Eleven [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.6		0.3
Interest Rate		1.79%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Twelve [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.6		$ 0.3
Interest Rate		1.79%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Thirteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Fair Value at period end	[1]	$ (0.2)
Interest Rate		1.164%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Fourteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Fair Value at period end	[1]	$ (0.2)
Interest Rate		1.1635%
Interest Rate Swap Fifteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Fair Value at period end	[1]	$ (0.2)
Interest Rate		1.164%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Sixteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.1
Interest Rate		1.159%

[1] As of September 30, 2015 and December 31, 2014, derivative valuations in their entirety were classified in Level 2 of the fair value hierarchy and we did not have any significant recurring fair value measurements related to derivative instruments using significant unobservable inputs (Level 3).