Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidated Statements of Changes in Stockholders' Equity [Abstract]
Cash dividends - per share (in dollars per share)	$ 0.90	$ 0.87	$ 0.84
Purchase of treasury shares (in shares)	675,535	1,047,152	3,288
Net issuance of shares to employee stock plans, including tax benefit (in shares)	502,585	581,400	386,692