Financial Instruments - Summary of Outstanding Interest Rate Swap (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Interest at a fixed rate	1.41%	1.41%
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional value	$ 40,000	$ 40,000
Interest rate swap description	Interest that various with the three-month LIBOR	Interest that various with the three-month LIBOR
June 2014 [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional value	15,000	15,000
Interest rate swap expiration date	2014-06	2014-06
June 2015 [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional value	$ 25,000	$ 25,000
Interest rate swap expiration date	2015-06	2015-06