INCOME TAXES (Components of income tax expense (benefit)) (Detail) - 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 income taxes:
Federal									$ 22,355	$ 18,699	$ 17,890
State									5,146	4,692	4,140
Total current									27,501	23,391	22,030
Deferred income taxes:
Federal									6,973	516	10
State									252	(167)	(13)
Total deferred									7,225	349	(3)
Total income tax expense (benefit)	$ 11,933	$ 8,229	$ 6,966	$ 7,598	$ 6,879	$ 6,734	$ 5,008	$ 5,119	$ 34,726	$ 23,740	$ 22,027