Income Taxes (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Tax Disclosure [Abstract]
Income tax expense	$ 83,850	$ 26,898	$ 120,499	$ 50,868
Effective tax rate	38.00%	39.00%	38.00%	38.00%
Federal statutory rate			35.00%	35.00%
State income tax expense	4,687	1,710	6,709	3,064
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	(1,027)	866		1,630
Tax benefit from a decrease in the valuation allowance	2,334		2,334	(1,800)
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	20,000		20,000
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation			2,893
Second component of tax deductible goodwill, net of tax			811
Tax Adjustments, Settlements, and Unusual Provisions			$ 447