Significant Components of Provision for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components Of Income Tax Expense Benefit [Line Items]
Current, Federal	$ 75,522	$ 65,461	$ 70,715
Current, State	11,852	10,084	10,236
Current, Foreign	669	638	860
Total current provision	88,043	76,183	81,811
Deferred, Federal	27,348	27,212	19,890
Deferred, State	5,375	3,131	2,645
Total deferred provision	32,723	30,343	22,535
Total tax provision	$ 120,766	$ 106,526	$ 104,346