Long-Term Debt - Summary of Interest Received and Paid under Term of Cash Flow Swap (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Derivatives, Fair Value [Line Items]
Receive Rate	One-month LIBOR
Variable Interest Rate	0.179%
Cash Flow Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	2.7
Pay Rate	7.10%
Receive Rate	one-month LIBOR + 1.50%
Maturing Date	Jul. 10, 2017
Variable Interest Rate	1.50%
Cash Flow Swap 1 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	8.5
Pay Rate	4.655%
Receive Rate	one-month LIBOR
Maturing Date	Dec. 10, 2017
Cash Flow Swap 2 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	7.3
Pay Rate	6.86%
Receive Rate	one-month LIBOR + 1.25%
Maturing Date	Aug. 01, 2017
Variable Interest Rate	1.25%
Cash Flow Swap 3 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	100.0
Pay Rate	3.28%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2015
Cash Flow Swap 4 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	100.0
Pay Rate	3.30%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2015
Cash Flow Swap 5 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	6.3
Pay Rate	6.41%
Receive Rate	one-month LIBOR + 1.25%
Maturing Date	Aug. 12, 2017
Variable Interest Rate	1.25%
Cash Flow Swap 6 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	50.0
Pay Rate	3.24%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2017
Cash Flow Swap 7 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	50.0
Pay Rate	3.07%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2017
Cash Flow Swap 8 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	100.0
Pay Rate	2.065%
Receive Rate	one-month LIBOR
Maturing Date	Jun. 30, 2017
Cash Flow Swap 9 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	100.0
Pay Rate	2.015%
Receive Rate	one-month LIBOR
Maturing Date	Jun. 30, 2017
Cash Flow Swap 10 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	200.0
Pay Rate	0.788%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2016
Cash Flow Swap 11 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	50.0
Pay Rate	1.32%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2017
Cash Flow Swap 12 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	250.0
Pay Rate	1.887%
Receive Rate	one-month LIBOR
Maturing Date	Jun. 30, 2018
Cash Flow Swap 13 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	25.0
Pay Rate	2.08%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2017
Cash Flow Swap 14 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	100.0
Pay Rate	1.56%
Receive Rate	one-month LIBOR
Maturing Date	Jul. 01, 2017