SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Information 3 (Details) $ in Thousands		12 Months Ended
	Jul. 09, 2015	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Operating Segments
Number of reportable operating segments | item		1
Reclassifications
Reclassification effect		$ 0
Adoption of New Accounting Standards
Deferral period of new accounting standard after amendments	1 year
Reduction in income tax expense		$ (12,137)	$ (10,233)	$ (7,779)
Minimum
Equity
Stock dividends rate reported by transferring the par value of the stock issued from retained earnings to common stock (as a percent)		20.00%
Maximum
Equity
Stock dividends rate reported by transferring the fair value, as of the ex-dividend date, of the stock issued from retained earnings to common stock and additional paid-in capital (as a percent)		20.00%
Parent Company
Adoption of New Accounting Standards
Reduction in income tax expense		$ 4,415	$ 2,989	$ 3,118
Restricted stock
Adoption of New Accounting Standards
Reduction in income tax expense		140
Stock option
Adoption of New Accounting Standards
Reduction in income tax expense		$ 185
Core deposit intangibles
Goodwill and Other Intangible Assets
Estimated useful lives of other intangible assets		10 years
Other customer relationship intangibles
Goodwill and Other Intangible Assets
Estimated useful lives of other intangible assets		10 years