Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Effective income tax rates	27.90%	27.30%	28.30%
Statutory federal tax rate	35.00%
State net operating loss carryforwards	$ 900,000
Change in valuation allowance, unrealized deferred tax assets	1,900,000
Gross amount of unrecognized tax benefits	4,347,000	4,101,000	3,898,000
Total amount of unrecognized tax benefits, net of associated deferred tax benefit that would impact effective tax rate, if recognized	$ 2,800,000	$ 2,700,000
Minimum
Income Taxes [Line Items]
State net operating loss carryforwards, expiration year	2013
Maximum
Income Taxes [Line Items]
State net operating loss carryforwards, expiration year	2032