Equity Compensation Plans and Equity (Details 4) (USD $)	1 Months Ended	12 Months Ended
	Aug. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Treasury Stock	Dec. 31, 2011 Treasury Stock	Dec. 31, 2010 Treasury Stock	Dec. 31, 2012 Retained Earnings	Dec. 31, 2012 Common Stock	Dec. 31, 2011 Common Stock	Dec. 31, 2010 Common Stock
Treasury Stock Activity
Authorized amount of common stock repurchase (in dollars)	$ 200,000,000
Treasury stock (in shares)		4,160,228	1,118,600		4,160,228	1,118,600			4,160,228	1,118,600
Amount of shares repurchased including transaction costs (in dollars)		162,077,000	38,098,000		162,077,000	38,098,000
Average cost of per share repurchased (in dollars per share)					$ 38.96	$ 34.06
Treasury shares cancelled and retired				5,278,828
Reduction due to retirement of treasury stock				200,200,000
Reduction in treasury stock due to retirement							$ 200,100,000	$ 100,000