Consolidated Statement of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Dividends (in dollars per share)	$ 0.13	[1]	$ 0.13	[1]	$ 0.13	[1]	$ 0.13	[1]	$ 0.12	[1]	$ 0.12	[1]	$ 0.12	[1]	$ 0.12	[1]	$ 0.52	[1]	$ 0.48	[1]	$ 0.44

[1] Per share amounts for the quarters and the full years have each been calculated separately. Accordingly, quarterly amounts may not sum up to the annual amounts because of differences in the average common shares outstanding during each period and, with regard to diluted per share amounts only, because of the inclusion of the effect of potentially dilutive securities only in the periods in which such effect would have been dilutive.