Shareholders' Equity Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Repurchases Authorized per Capital Plan	$ 393
Equity Repurchases per Capital Plan	$ 242
Stock Option
Common stock shares reserved for future issuance	12,700
Restricted Stock
Shares of non-vested restricted stock outstanding	1,910	2,140
Common Stock
Shares repurchased under equity repurchase program	5,300	5,400	7,500
Warrants
Number of warrants to purchase common stock outstanding	9,500
Number of shares of common stock issuable under outstanding warrants	8,500
Average exercise price for outstanding warrants	$ 29.43
Year of expiration for outstanding warrants	2018
Shares of common stock issued upon exercise of warrants	934	361	0
Common stock shares reserved for future issuance	8,500
Equity Repurchase Program | Common Stock
Shares repurchased under equity repurchase program	5,100	5,200	7,400
Average cost per share of shares repurchased under equity repurchase program	$ 45.65	$ 47.91	$ 38.63
Equity Repurchase Program | Warrants
Warrants repurchased under equity repurchase program	500
Average cost per warrant repurchased under the equity repurchase program	$ 20.70