CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Operating activities:
Net income	$ 28,276	$ 24,399	$ 58,593	$ 46,064
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			6,724	6,099
Provision for loan losses	1,633	1,733	1,505	3,730	$ 9,023
Stock based compensation expense			1,473	1,250
Tax benefits associated with share based compensation			57	252
Deferred Income Tax Expense (Benefit)			1,795	2,358
Origination of loans held for sale			(299,401)	(186,777)
Proceeds from sales of loans held for sale			278,290	186,211
Gains on sales of loans held for sale			(6,627)	(3,674)
Losses on sales of other real estate owned			173	106
Investment securities gains	(5)	0	(5)	(63)
Increase (Decrease) in Operating Capital [Abstract]
Net (increase) decrease in accrued interest receivable			(1,540)	(1,211)
Net decrease (increase) in other assets			(4,880)	(443)
Net increase (decrease) in accrued expenses and other liabilities			(6,126)	(2,239)
Other - net			1,162	2,712
Net cash provided by operating activities			31,193	54,375
Investing activities:
(Purchases) of other equity securities				(12,027)
Proceeds from other equity securities			18,699
Purchases of investments available-for-sale			(15,919)	(497)
Proceeds from sales of investment available-for-sale			0	994
Proceeds from maturities, calls and principal payments of investments available-for-sale			66,887	52,798
Net (increase)/ decrease in loans			19,979	(315,872)
Proceeds from the sales of other real estate owned			324	676
Proceeds from sales of loans previously held for investment			0	59,945
Acquisition of business activity, net of cash paid			0	32,552
Expenditures for premises and equipment			(2,456)	(6,788)
Net cash provided/ (used) by investing activities			87,514	(188,219)
Financing activities:
Net increase in deposits			474,869	263,322
Net increase/(decrease) in retail repurchase agreements and federal funds purchased			(176,825)	13,402
Proceeds from advances from FHLB			2,123,000	3,920,000
Repayment of advances from FHLB			(2,388,843)	(3,861,413)
Proceeds from issuance of common stock			746	829
Stock tendered for payment of withholding taxes			(702)	(760)
Dividends paid			(20,757)	(19,268)
Net cash provided/ (used) by financing activities			11,488	316,112
Net increase (decrease) in cash and cash equivalents			130,195	182,268
Cash and cash equivalents at beginning of period			101,481	112,500	112,500
Cash and cash equivalents at end of period	$ 231,676	$ 294,768	231,676	294,768	$ 101,481
Supplemental Disclosures:
Interest payments			43,348	26,587
Income tax payments			18,629	11,598
Transfer from loans to residential mortgage loans held for sale			0	60,043
Transfers from loans to other real estate owned			$ 414	$ 289