Employee Benefit Plans - Obligation and Funded Status of Defined Benefit Pension Plan and Retirement Plan (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Change in benefit obligation
Service cost	$ 843		$ 749		$ 523
Interest cost	1,160		1,167		1,043
Change in plan assets
Fair value of plan assets at beginning of year	14,687
Fair value of plan assets at end of year	18,367		14,687
Unrecognized loss included in accumulated other comprehensive loss
Amortization	1,093		1,147		430
Defined Benefit Pension and Other Postretirement Plans
Change in benefit obligation
Benefit obligation at beginning of year	31,142	[1]	28,605	[1]
Service cost	843	[1]	749	[1]
Interest cost	1,160	[1]	1,167	[1]
Actuarial (gain) loss	(3,372)	[1]	1,633	[1]
Benefits paid	(1,335)	[1]	(1,012)	[1]
Ending benefit obligation (December 31)	28,438		31,142	[1]
Change in plan assets
Fair value of plan assets at beginning of year	14,687		11,945
Return on assets	2,509		1,513
Employer contribution	2,506		2,241
Benefits paid	(1,335)	[1]	(1,012)	[1]
Fair value of plan assets at end of year	18,367		14,687
Funded status (under funded)	(10,071)		(16,455)
Amounts recognized in the consolidated balance sheet
Current liabilities	497		672
Non-current liabilities	9,574		15,783
Unrecognized loss included in accumulated other comprehensive loss
Unrecognized loss before tax, beginning balance	11,934		11,902
Amortization	(1,093)		(1,147)
Liability (gain) loss	(3,372)		1,633
Asset (gain) loss	(1,286)		(454)
Unrecognized loss before tax, ending balance	6,183		11,934
Tax impact	(2,321)		(4,466)
Unrecognized loss included in accumulated other comprehensive loss, net of tax	3,862		7,468
Prepaid benefit cost included in other assets	1,135		913
Accrued benefit cost included in other liabilities	$ 5,024		$ 5,433

[1] Projected benefit obligation equals the accumulated benefit obligation for the plans.