SHARE-BASED PAYMENT - Plan Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted shares
Restricted Shares - Shares
Nonvested at beginning of period (in shares)	1,171,018
Granted (in shares)	486,173
Vested (in shares)	(563,736)
Forfeited (in shares)	(8,079)
Nonvested at end of period (in shares)	1,085,376	1,171,018
Restricted Shares - Weighted Average Grant-date Fair Value
Nonvested at beginning of period (in dollars per share)	$ 37.32
Granted (in dollars per share)	54.52	$ 52.25	$ 41.15
Vested (in dollars per share)	30.81
Forfeited (in dollars per share)	41.17
Nonvested at end of period (in dollars per share)	$ 48.39	$ 37.32
Additional disclosures
Fair value, vested shares (in dollars)	$ 30,500	$ 29,600	$ 21,200
Unrecognized compensation
Unrecognized compensation for outstanding restricted shares/units	$ 28,700
Unrecognized compensation cost, period for recognition	3 years 1 month 6 days
Stock options
Options
Outstanding at beginning of period (in shares)	1,048,264
Granted (in shares)	0	0
Exercised (in shares)	(65,182)
Outstanding at end of period (in shares)	983,082	1,048,264
Exercisable at end of period (in shares)	945,506
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 19.76
Exercised (in dollars per share)	20.29
Outstanding at end of period (in dollars per share)	19.72	$ 19.76
Exercisable at end of period (in dollars per share)	$ 18.92
Weighted-Average Remaining Contract Life (Years)
Outstanding at end of period (in years)	4 years 7 months 6 days
Exercisable at end of period (in years)	4 years 6 months
Aggregate Intrinsic Value
Outstanding at end of period (in dollars)	$ 44,199
Exercisable at end of period (in dollars)	43,265
Intrinsic value of options exercised, (in dollars)	2,700	$ 13,500	400
Cash received from the exercise of options	0	$ 0	$ 0
Unrecognized compensation
Unrecognized compensation cost for outstanding options	$ 100
Unrecognized compensation cost, period for recognition	1 month 6 days
RSUs
Restricted Shares - Shares
Nonvested at beginning of period (in shares)	1,098,612
Granted (in shares)	295,851
Vested (in shares)	(488,787)	0
Forfeited (in shares)	(15,627)
Nonvested at end of period (in shares)	890,049	1,098,612
Restricted Shares - Weighted Average Grant-date Fair Value
Nonvested at beginning of period (in dollars per share)	$ 35.54
Granted (in dollars per share)	52.84	$ 49.72	$ 41.79
Vested (in dollars per share)	23.92
Forfeited (in dollars per share)	23.92
Nonvested at end of period (in dollars per share)	$ 47.87	$ 35.54
Additional disclosures
Fair value, vested shares (in dollars)	$ 26,600		$ 23,100
Unrecognized compensation
Unrecognized compensation for outstanding restricted shares/units	$ 6,500
Unrecognized compensation cost, period for recognition	3 years