Schedule of Reconciliation of Defined Benefit Pension Plan (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of plan assets at beginning of year	$ 87,940	$ 73,402
Actual return (loss) on plan assets	13,824	5,689
Employer contributions	7,786	14,065
Benefits paid	(4,946)	(4,541)
Administrative expenses	(530)	(675)
Fair value of plan assets at end of year	104,074	87,940	73,402
Benefit obligation at beginning of year	108,446	93,513
Service cost	1,144	1,162	1,140
Interest cost	4,659	5,047	4,958
Benefits paid	(4,946)	(4,541)
Actuarial (gain) loss	5,226	13,265
Benefit obligation at end of year	114,529	108,446	93,513
Other noncurrent liabilities	10,455	20,506
Total liability at end of year	10,455	20,506
Projected benefit obligation	114,529	108,446
Accumulated benefit obligation	112,675	106,609
Fair value of plan assets	$ 104,074	$ 87,940	$ 73,402