LEASES - Maturities of operating lease liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Maturities of operating lease liabilities as of June 30, 2019
2019	$ 3,088
2020	6,046
2021	5,946
2022	5,742
2023	4,759
Thereafter	21,124
Total operating lease payments	46,705
Less: Interest	(6,442)
Present value of operating lease liabilities	$ 40,263
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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