Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Held to Maturity, Fair value	$ 5,861.5	$ 5,227.5
Total Loans and Leases, unearned income	$ 93.4	$ 103.6
Preferred Stock, Par Value (in dollars per share)	$ 0	$ 0
Preferred Stock, Authorized	10,000,000	10,000,000
Preferred Stock, Outstanding	16,000	16,000
Common Stock, Par Value (in dollars per share)	$ 1.6667	$ 1.6667
Common Stock, Authorized	560,000,000	560,000,000
Common Stock, Outstanding	228,163,712	229,293,783
Treasury Stock, shares	17,007,812	15,877,741