INCOME TAXES - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current – federal									$ 27,714	$ 33,074	$ 28,749
Current - state									1,375	5,230	3,550
Deferred - federal									496	3,874	2,460
Deferred - state									878	(5,069)	(1,613)
Remeasurement of deferred tax assets and deferred tax liabilities at reduced federal corporate tax rate									0	13,625	0
Provision for income taxes	$ 7,017	$ 13,317	$ 2,423	$ 7,706	$ 22,063	$ 8,142	$ 10,315	$ 10,214	$ 30,463	$ 50,734	$ 33,146