Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Held to maturity, fair value	$ 10,778.7	$ 8,905.1
Total loans and leases, unearned income	$ 36.3	$ 41.2
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 1.6667	$ 1.6667
Common stock, authorized (in shares)	560,000,000	560,000,000
Common stock, outstanding (in shares)	227,421,128	228,605,485
Treasury stock, (in shares)	17,750,396	16,566,039
Series C Preferred Stock
Preferred stock, outstanding (in shares)	16,000	16,000
Series D Preferred Stock
Preferred stock, outstanding (in shares)	5,000	5,000