Share Repurchase Program (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Aug. 04, 2011
Share Repurchase Program (Textual) [Abstract]
Increase in share repurchase program authorization		$ 250.0
Share repurchase program authorization	650.0
Share repurchase program authorization date	Aug. 05, 2009
Common Stock
Class of Stock [Line Items]
Remaining value of common stock authorized for repurchase under the share repurchase program	$ 298.6