CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY, (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Stockholders Equity [Abstract]
Cash dividend declared, per share	$ 0.42	$ 0.42	$ 1.26	$ 1.26