Derivative Financial Instruments - Company's Derivative Instruments of Interest Rate Swaps (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Interest Rate Swap One
Derivative [Line Items]
Date Entered	2009-03
Notional Amount	$ 175,000
Fixed Interest Rate Paid	2.85%	[1]
Variable Interest Rate Received	1-month LIBOR
Effective Date	2011-02
Expiration Date	2014-02
Interest Rate Swap Two
Derivative [Line Items]
Date Entered	2011-08
Notional Amount	150,000
Fixed Interest Rate Paid	0.80%	[1]
Variable Interest Rate Received	1-month LIBOR
Effective Date	2012-04
Expiration Date	2015-01
Interest Rate Swap Three
Derivative [Line Items]
Date Entered	2011-12
Notional Amount	$ 175,000
Fixed Interest Rate Paid	1.60%	[1]
Variable Interest Rate Received	1-month LIBOR
Effective Date	2014-02
Expiration Date	2017-02

[1] plus applicable margin.