Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive (Income) Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Components of Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Line Items]
Net actuarial (gain) loss	$ (621)	$ 9,504	$ 3,328
Amortization of net actuarial loss	(2,718)	(1,803)	(1,917)
Prior service cost (credit)	0	0	(10,370)
Amortization of prior service cost (credit)	1,555	1,555	(28)
Settlement	(792)	(1,204)	0
Other comprehensive (income) loss	(2,576)	8,052	(8,987)
Total recognized in net periodic pension (benefit) cost and other comprehensive (income) loss	$ (2,790)	$ 7,153	$ (8,395)