Income Taxes - Reconciliation of Income Tax Expense Computed by Applying the United States Federal Income Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Provision of Income Taxes [Line Items]
Federal statutory income tax rate	35.00%
Computed "expected" tax expense	$ 192,638	$ 223,310	$ 197,424
Increase in income taxes resulting from:
State income taxes, net of Federal income tax benefit	8,111	13,318	9,054
Nondeductible stock compensation expense, net	12,061	12,877	10,254
Other, net	4,614	2,280	3,131
Income tax expense	$ 217,424	$ 251,785	$ 219,863