Stockholders' Equity Matters (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended												3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jun. 30, 2012	Apr. 30, 2012	Mar. 31, 2012	Jan. 31, 2012	Dec. 31, 2011	Oct. 31, 2011	Sep. 30, 2011	Jul. 31, 2011	Jun. 30, 2011	Apr. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Stockholders' Equity Note
Share repurchases authorized amount															$ 1,200,000
Remaining amount available under share repurchase program															66,035
Percentage of outstanding common stock authorized for repurchase															1.00%
Dividends declared (in dollars per share)		$ 0.2700		$ 0.2500		$ 0.2500		$ 0.2500		$ 0.2500		$ 0.1875	$ 0.2700	$ 0.2500	$ 0.5200	$ 0.4375
Dividends declared		46,336		42,791		43,180		46,877		50,694		37,601			89,161	88,225
Dividends paid ( in dollars per share)		$ 0.2700		$ 0.2500		$ 0.2500		$ 0.2500		$ 0.2500		$ 0.1875
Dividends paid	$ 46,336		$ 42,791		$ 43,180		$ 46,877		$ 50,694		$ 37,601				$ 85,971	$ 75,044