Summary of Interest Rate Swap Agreements Designated as Hedge Agreements (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Interest Rate Swaps [Line Items]
Nominal Amount	$ 450,000
Current Liability	5,268	[1]
Long-Term Liability	5,167	[2]
Estimated Total Fair Value at June 30, 2013	10,435
Interest Rate Swap One Agreements
Interest Rate Swaps [Line Items]
Nominal Amount	175,000
Effective Date	Dec. 01, 2010
Pay Rate	1.3975%
Receive Rate	1-Month LIBOR
Expiration Date	Sep. 01, 2015
Current Liability	1,916	[1]
Long-Term Liability	1,757	[2]
Estimated Total Fair Value at June 30, 2013	3,673
Interest Rate Swap Two Agreements
Interest Rate Swaps [Line Items]
Nominal Amount	175,000
Effective Date	Dec. 01, 2010
Pay Rate	1.40%
Receive Rate	1-Month LIBOR
Expiration Date	Sep. 01, 2015
Current Liability	1,934	[1]
Long-Term Liability	1,765	[2]
Estimated Total Fair Value at June 30, 2013	3,699
Interest Rate Swap Three Agreements
Interest Rate Swaps [Line Items]
Nominal Amount	100,000
Effective Date	Nov. 01, 2011
Pay Rate	1.715%
Receive Rate	1-Month LIBOR
Expiration Date	Apr. 01, 2016
Current Liability	1,418	[1]
Long-Term Liability	1,645	[2]
Estimated Total Fair Value at June 30, 2013	$ 3,063

[1] Included in accounts payable and accrued expenses on the condensed consolidated balance sheet as of June 30, 2013.

[2] Included in other long-term liabilities on the condensed consolidated balance sheet as of June 30, 2013.