Income Taxes (Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income taxes:
Federal									$ 75,945	$ 67,449	$ 74,109
State									10,397	16,046	16,224
Foreign									4,566	2,196	1,918
Total current income taxes									90,908	85,691	92,251
Deferred income taxes:
Federal									466	1,813	(19,550)
State									6,113	(114)	(4,206)
Foreign									(2,454)	(160)	441
Total deferred income taxes									4,125	1,539	(23,315)
Total income tax expense	$ 23,669	$ 25,034	$ 24,490	$ 21,840	$ 22,534	$ 22,519	$ 21,943	$ 20,234	$ 95,033	$ 87,230	$ 68,936