Income Taxes (Earnings Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit) [Abstract]
Domestic									$ 649,098	$ 545,527	$ 409,068
Foreign									25,057	29,554	21,572
Earnings before income taxes	$ 158,151	$ 175,836	$ 179,039	$ 161,129	$ 140,769	$ 155,319	$ 150,182	$ 128,811	$ 674,155	$ 575,081	$ 430,640