Derivatives - Fair Value of Derivative Instruments (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2017		Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Fair Value at period end	[1]	$ (5.6)		$ (4.3)
Interest Rate Swap One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		48.0
Fair Value at period end	[1]	$ 0.0		0.1
Interest Rate		1.12%
Maturity Date		Jan. 01, 2018
interest Rate Swap One prior year [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 28.1
Fair Value at period end	[1]			$ 0.0
Interest Rate				1.38%
Maturity Date		Jan. 02, 2017
Interest Rate Swap Two [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 Three [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 55.0
Fair Value at period end		$ 0.0	[1]	0.1
Interest Rate		1.12%
Maturity Date		Jan. 01, 2018
Interest Rate Swaps Four [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 30.0
Fair Value at period end		$ (0.1)	[1]	0.3
Interest Rate		1.78%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Five [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Fair Value at period end		$ (0.3)		(0.3)
Interest Rate		0.70%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Six [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ (0.1)		(0.2)
Interest Rate		1.78%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Seven [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ (0.1)		(0.2)
Interest Rate		1.78%
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]	$ (0.1)		(0.2)
Interest Rate		1.79%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Twenty Nine [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Interest Rate Swap twenty eight [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		25.0
Fair Value at period end	[1]	$ 0.1
Interest Rate		1.7525%
Maturity Date		Dec. 29, 2021
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]	$ (0.1)		(0.2)
Interest Rate		1.79%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Thirty [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
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]	$ (0.1)		(0.2)
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		$ 25.0
Fair Value at period end	[1]	$ 0.1		0.1
Interest Rate		1.16%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Twelve [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 25.0
Fair Value at period end	[1]	$ (0.1)		(0.1)
Interest Rate		1.16%
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]	$ (0.1)		(0.1)
Interest Rate		1.16%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Fourteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ (0.1)		0.0
Interest Rate		1.16%
Maturity Date		Jan. 02, 2019
Interest Rate Swap Fifteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.2		0.2
Interest Rate		1.23%
Maturity Date		Jun. 26, 2020
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]	$ 0.2		0.2
Interest Rate		1.23%
Maturity Date		Jun. 26, 2020
Interest Rate Swap Seventeen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.2		0.2
Interest Rate		1.23%
Maturity Date		Jun. 26, 2020
Interest Rate Swap Eighteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.2		0.2
Interest Rate		1.23%
Maturity Date		Jun. 26, 2020
Interest Rate Swap Nineteen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end	[1]	$ 0.2		0.2
Interest Rate		1.24%
Maturity Date		Jun. 26, 2020
Interest Rate Swap Twenty [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 9.0
Fair Value at period end		$ 0.2	[1]	(0.2)
Interest Rate		1.19%
Maturity Date		Feb. 01, 2021
Interest Rate Swap Twenty One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 35.0
Fair Value at period end		$ 0.9	[1]	(0.9)
Interest Rate		1.013%
Maturity Date		Mar. 01, 2021
Interest Rate Swap Twenty Three [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end		$ 0.5	[1]	(0.5)
Interest Rate		1.0145%
Maturity Date		Mar. 01, 2021
Interest Rate Swap Twenty Two [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 35.0
Fair Value at period end		$ 0.9	[1]	(0.9)
Interest Rate		1.016%
Maturity Date		Mar. 01, 2021
Interest Rate Forward Starting Swap One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 48.0
Fair Value at period end	[1]	$ 0.5		0.7
Interest Rate		1.42%
DerivativeEffectiveDate		Jan. 02, 2018
Maturity Date		Feb. 01, 2021
Interest Rate Swap Twenty Six [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 50.0
Interest Rate Swap Twenty Seven [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		25.0
Interest Rate Swap Twenty Five [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		20.0
Fair Value at period end		$ 0.5	[1]	(0.5)
Interest Rate		1.018%
Maturity Date		Mar. 01, 2021
Interest Rate Swap Twenty Four [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(in millions of dollars) Notional Value		$ 20.0
Fair Value at period end		$ 0.5	[1]	$ (0.5)
Interest Rate		1.016%
Maturity Date		Mar. 01, 2021

[1] As of June 30, 2017 and December 31, 2016, 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).