Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock option exercises/deferred stock unit conversions, shares	321,266	594,231	1,319,786
Non-vested stock awards, shares	15,790	7,620	13,040
Non-vested stock units, shares	38,200	24,430	24,970
Stock issued during period, shares, acquisitions	0	2,000,000	0
Issuance of preferred stock, shares	0	0	6,000,000
Purchase of treasury stock, shares	1,504,146	18,871	2,245,572
Approximate cash dividends declared on preferred stock, per share	$ 1.34	$ 1.34	$ 1.12
Cash dividends - common stock, per share	$ 2.10	$ 2.03	$ 1.98