STOCKHOLDERS' EQUITY - Common Stock (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity
Shares outstanding	47,828,079	47,487,510	47,059,458
Purchase of common stock	(123,577)	(260,088)	(270,467)
Shares issued under stock incentive plan, net of awards surrender to pay applicable taxes	192,050	218,458	319,773
Exercise of stock options	202,500	377,671	375,718
Shares issued to Board of Directors in lieu of cash	3,276	4,528	3,028
Shares outstanding	48,102,328	47,828,079	47,487,510