Income Taxes (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense	$ 36,649	$ 23,970
Effective tax rate	37.00%	36.00%
Federal statutory rate	35.00%	35.00%
State income tax expense	2,022	1,354
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1,060	764
Tax (benefit) expense from decrease (increase) in valuation allowance		(2,015)
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	19,000
Adjustment to paid-in capital for excess tax benefits from share-based compensation	1,333
Second component of tax deductible goodwill, net of tax	406
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount	$ 28,000