PARENT COMPANY ONLY FINANCIAL STATEMENTS - CONDENSED STATEMENT OF OPERATIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
INCOME—Interest income	$ 172,250	$ 155,544	$ 108,554
EXPENSE — Subordinated debentures	4,216	1,182	227
Provision for loan losses	14,360	64,700	17,864
Total noninterest expense	84,099	84,498	66,178
INCOME (LOSS) BEFORE INCOME TAXES	61,100	(1,374)	25,753
BENEFIT FOR INCOME TAXES	(26,964)	402	(10,314)
NET INCOME (LOSS)	34,136	(972)	15,439
Green Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
INCOME—Interest income	138	67	39
Loss on held-for-sale loans	(138)	0	0
Dividends from bank subsidiary	1,000	0	0
Total income	1,000	67	39
EXPENSE — Subordinated debentures	4,216	1,182	227
Provision for loan losses	10,536	0	0
General and administrative	3,746	2,806	3,293
Total noninterest expense	18,498	3,988	3,520
LOSS BEFORE EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARY AND INCOME TAXES	(17,498)	(3,921)	(3,481)
EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARY, NET OF TAX	44,427	1,577	17,995
INCOME (LOSS) BEFORE INCOME TAXES	26,929	(2,344)	14,514
BENEFIT FOR INCOME TAXES	7,207	1,372	925
NET INCOME (LOSS)	$ 34,136	$ (972)	$ 15,439