Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock option exercises/deferred stock unit conversions, shares	1,509,121	321,266	594,231
Non-vested stock awards, shares	0	15,790	7,620
Stock issued during period, shares, acquisitions	0	0	2,000,000
Purchase of treasury stock, shares	17,233	1,504,146	18,871
Approximate cash dividends declared on preferred stock, per share	$ 1.34	$ 1.34	$ 1.34
Cash dividends - common stock, per share	$ 2.15	$ 2.10	$ 2.03