Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Shares repurchased (in shares)	701,899	90,415	79,396
Shares issued for stock-based awards (in shares)	198,694	376,142	202,882
Dividends on common stock (in dollars per share)	$ 1.09	$ 0.97	$ 0.86