Common and Preferred Shares and Warrants (Details Textuals) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 12, 2015
Common And Preferred Shares And Warrants (Textuals) [Abstract]
Common share repurchases authorized				150,000,000
Common shares repurchased	58,800,000	49,000,000
Cost basis of common stock repurchased	$ 4,480,000,000	$ 4,389,000,000	$ 3,943,000,000
Commissions paid included in cost basis of common stock repurchased	$ 1,100,000	$ 1,000,000
Common shares remaining under share repurchase authorizations	106,000,000
Shares held as treasury shares	3,000,000	3,200,000	3,500,000
Cost basis of treasury stock	$ 242,000,000	$ 280,000,000	$ 260,000,000
Preferred shares, authorized	20,000,000	20,000,000
Preferred shares, par value	$ 1.67	$ 1.67
Preferred stock, shares issued	1,600	750	0
Preferred stock, shares outstanding	1,600	750	0
Depositary Shares, Redemption Amount	$ 1,000
Warrants, issued and outstanding	0	0	0
Liquidation price per share	$ 1,000,000