INCOME TAXES - Reconciliation of Income Tax Provision To Total Income Taxes At Statutory Federal Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes
Federal income taxes, at statutory tax rate									$ 28,159	$ 27,463	$ 24,979
State income taxes, net of federal benefit									3,947	3,962	3,459
Nondeductible expenses									602	538	503
Other-net									(366)	(323)	(254)
Net provision	$ 8,890	$ 8,825	$ 8,540	$ 6,087	$ 9,258	$ 8,831	$ 7,955	$ 5,596	$ 32,342	$ 31,640	$ 28,687