Deferred Gain and Related Tax on Derivative Instrument (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Deferred gains (losses) in AOCI	$ 1,076	$ (670)
Tax on deferred gains (losses) in AOCI	(175)	232
Deferred gains (losses) in AOCI, net of taxes	901	(438)
Deferred gains (losses) expected to be reclassified to "Revenues" from AOCI during the next twelve months	$ 1,076