SHARE-BASED AWARDS - RESTRICTED STOCK UNIT ACTIVITY (Details) - Restricted Stock Units shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Non-vested restricted stock unit activity
Outstanding, beginning of period (in shares)	720
Granted (in shares)	457
Vested (in shares)	(479)
Cancelled (in shares)	(12)
Outstanding, end of period (in shares)	686
Weighted Average Grant-Date Fair Value
Outstanding, weighted average grant-date fair value, beginning of period (in dollars per share) | $ / shares	$ 33.35
Granted, weighted average grant-date fair value (in dollars per share) | $ / shares	31.76
Vested, weighted average grant-date fair value (in dollars per share) | $ / shares	27.35
Cancelled, weighted average grant-date fair value (in dollars per shares) | $ / shares	37.24
Outstanding, weighted average grant-date fair value, end of period (in dollars per shares) | $ / shares	$ 36.41
2007 Plan
Non-vested restricted stock unit activity
Outstanding, beginning of period (in shares)	701
Granted (in shares)	153
Vested (in shares)	(470)
Cancelled (in shares)	(7)
Outstanding, end of period (in shares)	377
2016 Plan
Non-vested restricted stock unit activity
Outstanding, beginning of period (in shares)	19
Granted (in shares)	304
Vested (in shares)	(9)
Cancelled (in shares)	(5)
Outstanding, end of period (in shares)	309