INCOME TAXES - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current – federal									$ 33,074	$ 28,749	$ 15,215
Current - state									5,230	3,550	1,026
Deferred - federal									3,874	2,460	(344)
Deferred - state									(5,069)	(1,613)	0
Remeasurement of deferred tax assets and deferred tax liabilities at reduced federal corporate tax rate									13,625	0	0
Provision for income taxes	$ 22,063	$ 8,142	$ 10,315	$ 10,214	$ 6,987	$ 10,364	$ 9,671	$ 6,124	$ 50,734	$ 33,146	$ 15,897