STOCKHOLDERS' EQUITY, Repurchase of Common Stock (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Repurchase of common stock [Abstract]
Number of shares authorized to be repurchased (in shares)	3,763,038
Aggregate number of shares repurchased since inception (in shares)	2,174,017
Number of shares remaining in treasury (in shares)	0	0
Number of shares acquired under the stock repurchase plan and subsequently reissued (in shares)	23,182	24,912
Treasury stock acquired, average cost (in dollars per share)	$ 82.19	$ 63.76