INCOME TAXES - Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current, federal taxes	$ 7,683	$ 16,569	$ 31,132	$ 29,859
Current, state taxes	1,145	406	3,894	1,991
Total current income taxes	8,828	16,975	35,026	31,850
Deferred, federal taxes	12,952	14,088	28,110	38,238
Deferred, state taxes	374	2,115	757	(809)
Total deferred income taxes	13,326	16,203	28,867	37,429
Income taxes	$ 22,154	$ 33,178	$ 63,893	$ 69,279
Statutory tax rate	21.00%	35.00%	21.00%	35.00%
Effective tax rate	18.00%	29.90%	19.00%	28.40%