Pension and Profit Sharing Plans - Benefit Obligation Activity and Fair Value of Plan Assets and Statement of Funded Status (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 1,113	$ 1,139	$ 1,159
Employer contributions	2,000	1,500
Fair value of plan assets at December 31	21,110
Reconciliation of benefit obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at January 1	24,608	22,263
Interest cost on projected benefit obligation	1,113	1,139
Actuarial loss (gain)	3,470	2,320
Benefits paid	(1,353)	(1,114)
Benefit obligation at December 31	27,838	24,608
Reconciliation of fair value of plan assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	18,076	17,184
Actual return on plan assets	2,387	506
Employer contributions	2,000	1,500
Benefits paid	(1,354)	(1,114)
Fair value of plan assets at December 31	21,110	18,076
Funded status at December 31	$ (6,728)	$ (6,532)