CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends on common stock (in dollars per share)	$ 0.69	$ 0.54	$ 0.41