NET INCOME PER SHARE (DILUTED SHARES TABLE) (DETAILS) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares used in basic earnings per share calculation	46,386	47,081	47,873	48,368	48,439	48,345	48,325	48,370	47,423	48,370	49,297
Effect of dilutive securities:
Stock options									10	275	413
Restricted stock units									286	338	392
Performance-based restricted stock units									17	28	0
Total effects of dilutive securities									313	641	805
Shares used in dilutive earnings per share calculation	46,677	47,315	48,221	48,746	48,853	48,936	49,064	49,158	47,736	49,011	50,102