Benefit Plans - Status of Company's Supplemental Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in benefit obligation:
Benefit obligation at beginning of year	$ 14,038	$ 12,688	$ 11,414
Service cost	521	506	429
Interest cost	673	642	638
Amendments
Actuarial loss	33	895	819
Benefits paid	(900)	(693)	(612)
Benefit obligation at end of year	14,365	14,038	12,688
Change in plan assets:
Fair value of plan assets at beginning of year
Actual return on assets
Employer contribution	900	693	612
Benefits paid	(900)	(693)	(612)
Fair value of plan assets at end of year
Funded status at year end	$ (14,365)	$ (14,038)	$ (12,688)