Income Taxes (Income Tax Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current income tax expense	$ 60,533	$ 52,932	$ 63,575
Deferred income tax expense (benefit)	8,167	4,644	(9,854)
Income tax expense	$ 68,700	$ 57,576	$ 53,721