CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Reacquisition on open market, shares	331,632	0	398,095
Exercise of stock options, net of shares reacquired	620,927	681,173	302,521