INCOME TAXES (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
Current expense
Federal									$ 28,852	$ 26,549	$ 11,946
State									9,278	8,883	5,052
Total current expense									38,130	35,432	16,998
Deferred expense (benefit)
Federal									7,953	153	8,466
State									1,258	(158)	1,754
Total deferred expense (benefit)									9,211	(5)	10,220
Total expense	$ 14,915	$ 12,681	$ 10,731	$ 9,014	$ 7,698	$ 9,793	$ 9,508	$ 8,428	$ 47,341	$ 35,427	$ 27,218