Income Taxes (Income Tax Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Income Taxes [Abstract]
Current income tax expense	$ 20,052	$ 12,792
Deferred income tax benefit	(2,539)	(139)
Income tax expense as reported	$ 17,513	$ 12,653
Effective tax rate	22.30%	19.60%