CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY, (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Stockholders Equity [Abstract]
Cash dividend declared, per share	$ 0.27	$ 0.42	$ 0.58	$ 0.84