CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities:
Net income	$ 24,399	$ 14,741	$ 46,064	$ 29,853
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			6,099	3,967
Provision for loan losses	1,733	1,322	3,730	1,516	$ 2,977
Stock based compensation expense			1,250	1,052
Tax benefits associated with share based compensation			252	692
Deferred Income Tax Expense (Benefit)			2,358	(540)
Origination of loans held for sale			(186,777)	(70,736)
Proceeds from sales of loans held for sale			186,211	79,489
(Gains)/ losses on sales of loans held for sale			(3,674)	(1,443)
(Gains) losses on sales of other real estate owned			106	(17)
Investment securities gains	0	(1,273)	(63)	(1,275)
Increase (Decrease) in Operating Capital [Abstract]
Net (increase) decrease in accrued interest receivable			(1,211)	(321)
Net increase in other assets			(443)	(1,506)
Net increase (decrease) in accrued expenses and other liabilities			(2,239)	(4,069)
Other - net			2,712	3,605
Net cash provided by operating activities			54,375	40,267
Investing activities:
Proceeds of other equity securities				4,681
Purchases of investments held-to-maturity			(12,027)
Purchases of investments available-for-sale			(497)	(115,028)
Proceeds from sales of investment available-for-sale			994	2,251
Proceeds from maturities, calls and principal payments of investments held-to-maturity			0	0
Proceeds from maturities, calls and principal payments of investments available-for-sale			52,798	70,361
Net increase in loans			(315,872)	(223,705)
Proceeds from the sales of other real estate owned			676	759
Proceeds from sales of loans held for investment			59,945	18,222
Acquisition of business activity, net of cash paid			32,552	0
Expenditures for premises and equipment			(6,788)	(2,395)
Net cash (used) in investing activities			(188,219)	(244,854)
Financing activities:
Net increase in deposits			263,322	307,901
Net increase/(decrease) in retail repurchase agreements and federal funds purchased			13,402	2,193
Proceeds from advances from FHLB			3,920,000	2,220,000
Repayment of advances from FHLB			(3,861,413)	(2,340,000)
Retirement of subordinated debt			0	(30,000)
Proceeds from issuance of common stock			829	817
Stock tendered for payment of withholding taxes			(760)	(952)
Repurchase of common stock			0	0
Dividends paid			(19,268)	(12,561)
Net cash provided by financing activities			316,112	147,398
Net increase (decrease) in cash and cash equivalents			182,268	(57,189)
Cash and cash equivalents at beginning of period			112,500	134,125	134,125
Cash and cash equivalents at end of period	$ 294,768	$ 76,936	294,768	76,936	$ 112,500
Supplemental Disclosures:
Interest payments			26,587	12,391
Income tax payments			11,598	16,287
Transfer of Investments Held-to-maturity to Available For Sale Securities			0	0
Transfer from loans to residential mortgage loans held for sale			60,043	18,053
Transfers from loans to other real estate owned			$ 289	$ 288