Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Dividends declared per share	$ 0.270	$ 0.240	$ 0.220
Purchase of common stock, shares	0	0	225,000
Equity compensation activity, shares	242,253	168,219	185,382