Supplemental Information to Consolidated Statements of Cash Flows - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flow Supplemental Disclosures [Line Items]
Restricted stock surrendered, in values	$ 103,000	$ 1,263,000	$ 177,000
Executive officer
Cash Flow Supplemental Disclosures [Line Items]
Restricted stock surrendered, (in shares)	943	57,096
Restricted stock surrendered, in values	100,000	1,000,000
Employees
Cash Flow Supplemental Disclosures [Line Items]
Restricted stock surrendered, (in shares)	13,050	13,986	9,967
Restricted stock surrendered, in values	200,000	200,000	200,000
Restricted Stock Vested
Cash Flow Supplemental Disclosures [Line Items]
Tax benefit from vesting of restricted stock	(100,000)	400,000
Restricted Stock
Cash Flow Supplemental Disclosures [Line Items]
Restricted stock surrendered, (in shares)	13,993
Restricted stock surrendered, in values	200,000
Tax benefit from vesting of restricted stock	114,000	(909,000)	1,788,000
Tax deficiency from vesting of restricted stock			$ 700,000