Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Stockholders' Equity [Abstract]
Stock option exercises/stock unit conversions (shares)	19,232	22,724	447,831	774,799
Treasury stock, shares, acquired	0	1,134,966	601	1,135,435
Approximate cash dividends declared on preferred stock, per share	$ 0.34	$ 0.34	$ 1.01	$ 1.01
Cash dividends declared on common stock, per share	$ 0.67	$ 0.57	$ 1.91	$ 1.68