Stockholders' Equity (Changes To Equity) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Common Shares Outstanding [Roll Forward]
Common shares outstanding at January 1		196,086,090	198,830,351	203,551,496
Issuance of restricted stock, excluding restricted stock with performance feature		447,534	376,622	292,855
Vesting of performance units		136,896	416,111	210,819
Vesting of restricted stock with performance feature		43,774	77,430	15,141
Forfeitures of restricted stock		(51,332)	(76,107)	(15,794)
Purchase of treasury stock	[1]	(16,428,574)	(3,538,317)	(5,224,166)
Common shares outstanding at December 31		180,234,388	196,086,090	198,830,351
Shares withheld for the payment of taxes		151,967	279,680	235,922
Authorized share repurchase		$ 1,000.0
Stock repurchase program, value		308.2
Value of shares withheld related to tax withholding for share-based compensation		$ 6.2	$ 11.4	$ 11.3

[1] Includes 151,967, 279,680 and 235,922 shares, respectively, withheld under the terms of stock-based compensation agreements to provide funds for the payment of payroll and income taxes due at the vesting of share-based awards, as well as other stock repurchases under separate authority from our Board of Directors.