GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Carrying amount:
Total carrying amount	$ 126,066	$ 126,066
Accumulated amortization:
Total accumulated amortization	(64,574)	(51,967)
Total intangible assets, net	61,492	74,099
Customer service agreements
Carrying amount:
Total carrying amount	125,960	125,960
Accumulated amortization:
Total accumulated amortization	(64,520)	(51,923)
Other
Carrying amount:
Total carrying amount	106	106
Accumulated amortization:
Total accumulated amortization	$ (54)	$ (44)