Components of Net Periodic Benefits Cost (Benefit) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Net gain on curtailment of nonqualified pension plan			$ (690)
SERP II
Defined Benefit Plan Disclosure [Line Items]
Service cost	18	67	54	201
Interest cost	40	61	119	183
Amortization of prior service costs	3	21	10	62
Amortization of net loss	13	22	39	68
Net gain on curtailment of nonqualified pension plan			(690)
Net periodic benefit cost	74	171	(468)	514
QDBP
Defined Benefit Plan Disclosure [Line Items]
Interest cost	371	394	1,114	1,183
Expected return on plan assets	(745)	(701)	(2,236)	(2,103)
Amortization of net loss	431	447	1,293	1,340
Net periodic benefit cost	57	140	171	420
PRBP
Defined Benefit Plan Disclosure [Line Items]
Interest cost	8	9	22	27
Amortization of transition obligation		7		20
Amortization of net loss	19	19	58	58
Net periodic benefit cost	$ 27	$ 35	$ 80	$ 105