INCOME TAXES - Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Current, federal taxes	$ 17,700	$ 6,688
Current, state taxes	1,704	499
Total current income taxes	19,404	7,187
Deferred, federal taxes	1,902	1,690
Deferred, state taxes	(38)	(2,393)
Total deferred income taxes	1,864	(703)
Income taxes	$ 21,268	$ 6,484
Statutory tax rate	21.00%	35.00%
Effective tax rate	19.70%	22.00%