LEASES - Operating Leases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Leases
Cumulative effect adjustment for adoption of ASU 2016-02					$ (1,002)
Operating lease cost	$ 2,000		$ 5,600
Rent expense		$ 1,700		$ 4,900
Operating lease right-of-use assets	$ 22,700		$ 22,700
Operating lease, right-of-use asset, Statement of Financial Position	us-gaap:OtherAssets		us-gaap:OtherAssets
Operating lease liabilities	$ 28,879		$ 28,879
Operating lease liability, Statement of Financial Position	us-gaap:AccountsPayableAndOtherAccruedLiabilities		us-gaap:AccountsPayableAndOtherAccruedLiabilities
Operating leases, weighted average remaining lease term	4 years 1 month 6 days		4 years 1 month 6 days
Operating lease, weighted average discount rate (as a percent)	4.74%		4.74%
Retained Earnings
Leases
Cumulative effect adjustment for adoption of ASU 2016-02					$ (1,002)