PARENT COMPANY FINANCIAL DATA Condensed Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets [Abstract]
Cash and cash equivalents	$ 65,312	$ 29,081
Investment securities available for sale	672,421	404,388
Deferred tax asset, net	75,449	56,816
Accrued interest receivable and other assets	81,327	38,118
Total assets	4,266,309	2,122,713
Liabilities and Equity [Abstract]
Long-term debt	180,164	72,921
Accrued interest payable and other liabilities	30,479	13,002
Total liabilities	3,708,507	1,884,654
Total stockholders' equity	557,802	140,800
Total liabilities and shareholders' equity	4,266,309	2,122,713
Parent Company
Assets [Abstract]
Cash and cash equivalents	2,825	631	53	12,193
Investment securities available for sale	1,069	0
Investment in subsidiaries	615,570	140,233
Deferred tax asset, net	650	0
Accrued interest receivable and other assets	2,286	19
Total assets	622,400	140,883
Liabilities and Equity [Abstract]
Long-term debt	62,481	0
Accrued interest payable and other liabilities	2,117	83
Total liabilities	64,598	83
Total stockholders' equity	557,802	140,800
Total liabilities and shareholders' equity	$ 622,400	$ 140,883