Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	PREFERRED STOCK	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	TREASURY STOCK	Series C Preferred Stock [Member] PREFERRED STOCK
Balance, beginning of period at Dec. 31, 2012		$ 0.0	$ 408.6	$ 1,012.7	$ 6,702.7	$ (283.0)	$ (314.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Preferred Stock, Series C								$ 0.0
Treasury Stock Transactions – Stock Options and Awards				(55.0)			201.2
Stock Options and Awards – Amortization				75.0
Stock Options and Awards – Tax Benefits	$ 3.0			3.0
Net Income	731.3				731.3
Dividends Declared – Common Stock					(299.2)
Dividends Declared – Preferred Stock					0.0
Net Unrealized Gains (Losses) on Securities Available for Sale	(95.0)					(95.0)
Net Unrealized (Losses) Gains on Cash Flow Hedges	4.3					4.3
Foreign Currency Translation Adjustments	(3.4)					(3.4)
Pension and Other Postretirement Benefit Adjustments	132.8					132.8
Stock Purchased							(310.0)
Balance, end of period at Dec. 31, 2013	7,912.0	0.0	408.6	1,035.7	7,134.8	(244.3)	(422.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Preferred Stock, Series C								388.5
Treasury Stock Transactions – Stock Options and Awards				(71.1)			198.7
Stock Options and Awards – Amortization				77.5
Stock Options and Awards – Tax Benefits	8.8			8.8
Net Income	811.8				811.8
Dividends Declared – Common Stock					(311.7)
Dividends Declared – Preferred Stock					(9.5)
Net Unrealized Gains (Losses) on Securities Available for Sale	21.6					21.6
Net Unrealized (Losses) Gains on Cash Flow Hedges	(7.6)					(7.6)
Foreign Currency Translation Adjustments	(8.8)					(8.8)
Pension and Other Postretirement Benefit Adjustments	(80.6)					(80.6)
Stock Purchased							(480.7)
Balance, end of period at Dec. 31, 2014	8,448.9	388.5	408.6	1,050.9	7,625.4	(319.7)	(704.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Preferred Stock, Series C								$ 0.0
Treasury Stock Transactions – Stock Options and Awards				(74.0)			168.1
Stock Options and Awards – Amortization				77.7
Stock Options and Awards – Tax Benefits	17.7			17.7
Net Income	973.8				973.8
Dividends Declared – Common Stock					(333.0)
Dividends Declared – Preferred Stock					(23.4)
Net Unrealized Gains (Losses) on Securities Available for Sale	(58.6)					(58.6)
Net Unrealized (Losses) Gains on Cash Flow Hedges	1.7					1.7
Foreign Currency Translation Adjustments	(15.9)					(15.9)
Pension and Other Postretirement Benefit Adjustments	19.8					19.8
Stock Purchased							(496.9)
Balance, end of period at Dec. 31, 2015	$ 8,705.9	$ 388.5	$ 408.6	$ 1,072.3	$ 8,242.8	$ (372.7)	$ (1,033.6)