LEASES - Maturities of operating lease liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Maturities of operating lease liabilities as of March 31, 2019
2019	$ 4,532
2020	5,927
2021	5,824
2022	5,617
2023	4,630
Thereafter	20,566
Total operating lease payments	47,096
Less: Interest	(6,642)
Present value of operating lease liabilities	$ 40,454
Maturities of operating lease liabilities as of December 31, 2018
2019		$ 7,248
2020		6,504
2021		6,185
2022		5,903
2023		4,695
Thereafter		18,687
Total operating lease payments		$ 49,222

Amount of lessee's undiscounted obligation for lease payments for operating lease.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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