Earnings Per Common Share - Textual (Details) $ / shares in Units, $ in Millions		1 Months Ended						3 Months Ended	12 Months Ended
	Jul. 17, 2014 $ / shares	Jan. 31, 2016 $ / shares	Oct. 31, 2015 $ / shares	Jul. 31, 2015 $ / shares	Jan. 31, 2014 $ / shares	Jan. 16, 2014 USD ($) $ / shares shares	Jul. 31, 2013 $ / shares	Mar. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Feb. 14, 2014 USD ($)	Feb. 28, 2013 USD ($)	Dec. 31, 2012 $ / shares shares	Oct. 31, 2011 USD ($)	Sep. 30, 2009 yr $ / shares shares	Oct. 31, 2006 $ / shares shares	Jan. 31, 2004 shares
Earnings Per Common Share (Textual) [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share									100,000	100,000
Payments for Repurchase of Common Stock | $									$ 45.3	$ 43.1	$ 234.1
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.21			$ 0.23			$ 0.18		$ 0.88	$ 0.78	$ 0.36
Class of Warrant or Right, Outstanding						0				2,900,000				10,000,000				10,000,000
Stock Warrants Issued, Potential Number of Common Stock Shares																	2,000,000
Stock Warrants Issued, Exercise Price | $ / shares						$ 32.16				$ 32.50				$ 32.50		$ 41.40
Common Stock, Dividends, Per Share, Cash Paid | $ / shares					$ 0.18
Stock Warrants Issued, Exercise Rate						0.2021
Proceeds from exercising stock warrants | $						$ 6.3			$ 0.0	$ 6.3	$ 15.3
Common Stock Shares Issued Under Consolidated Securities Action Settlement																5,000,000
Common Stock Warrants Issued Under Consolidated Securities Action Settlement																8,200,000
Stock Warrants Issued, Term | yr																7
Convertible Debenture [Member]
Earnings Per Common Share (Textual) [Abstract]
Debt Instrument, Interest Rate, Stated Percentage																		3.25%
Common Stock [Member]
Earnings Per Common Share (Textual) [Abstract]
Stock Repurchase Program, Authorized Amount | $										$ 200.0		$ 250.0	$ 350.0		$ 125.0
Repurchase of common stock, Shares								9,100,000	1,300,000	1,300,000
Treasury Stock Acquired, Average Cost Per Share | $ / shares								$ 25.50
Repurchase of Common Stock | $								$ 234.1
Payments for Repurchase of Common Stock | $									$ 45.3	$ 43.1
Dividends Payable, Current | $									$ 21.3	$ 18.6
Stock Warrants Issued, Exercise Price | $ / shares																	$ 32.50
Common Stock, Dividends, Per Share, Cash Paid | $ / shares			$ 0.23
Stock warrants exercised, Shares						200,000					500,000
Subsequent Event [Member] | Common Stock [Member]
Earnings Per Common Share (Textual) [Abstract]
Common Stock, Dividends, Per Share, Cash Paid | $ / shares		$ 0.23