Benefit Plans - Change in Projected Benefit Obligation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 161,065	$ 135,678
Service cost	7,104	7,338	6,018
Interest cost	6,645	6,516	6,242
Plan amendments	119	944
Actuarial (gain) loss	(13,003)	14,326
Curtailments	(12,981)
Benefits paid	(3,915)	(3,737)
Projected benefit obligation at end of year	145,034	161,065	135,678
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	138,857	95,746
Actual return on plan assets	24,723	11,516
Employer contributions	25,245	35,332
Benefits paid	(3,915)	(3,737)
Fair value of plan assets at end of year	184,910	138,857	95,746
Funded status of the plan	39,876	(22,208)
Liability recognized	39,876	(22,208)
Accumulated benefit obligation	$ 145,034	$ 144,390