CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 100,864	$ 53,209	$ 48,250
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	12,516	7,976	7,958
Provision for loan losses	9,023	2,977	5,546
Stock based compensation expense	2,645	2,164	2,139
Deferred Income Tax Expense (Benefit)	5,655	6,089	349
Origination of loans held for sale	(416,337)	(142,877)	(196,726)
Proceeds from sales of loans held for sale	441,023	149,367	239,705
(Gains)/ losses on sales of loans held for sale	(11,699)	(3,403)	(3,877)
(Gains) losses on sales of other real estate owned	200	(68)	48
Tax benefits associated with share based compensation	299	1,809	125
Investment securities gains	(190)	(1,273)	(1,932)
Increase (Decrease) in Operating Capital [Abstract]
Net (increase) decrease in accrued interest receivable	(2,622)	(891)	(1,146)
Net decrease (increase) in other assets	5,020	(9,829)	(5,134)
Net increase (decrease) in accrued expenses and other liabilities	(2,721)	(1,007)	(2,932)
Other - net	3,970	5,174	(1,873)
Net cash provided by operating activities	147,646	69,417	90,500
Investing activities:
(Purchases) of other equity securities	(8,784)		(4,758)
Proceeds from other equity securities		576
Purchases of investments held-to-maturity	0	0	0
Purchases of investments available-for-sale	(161,349)	(125,028)	(287,211)
Proceeds from sales of investment available-for-sale	117,354	2,251	40,863
Proceeds from maturities, calls and principal payments of investments held-to-maturity	0	0	5,004
Proceeds from maturities, calls and principal payments of investments available-for-sale	106,114	123,762	298,803
Net increase in loans	(641,521)	(427,773)	(469,942)
Proceeds from the sales of other real estate owned	1,151	1,275	1,393
Proceeds from sales of loans previously held for investment	59,945	40,031	0
Acquisition of business activity, net of cash acquired	32,487	0	(1,347)
Expenditures for premises and equipment	(10,401)	(7,441)	(5,798)
Net cash provided/ (used) by investing activities	(505,004)	(392,347)	(422,993)
Financing activities:
Net increase in deposits	340,376	386,118	313,814
Net increase/(decrease) in retail repurchase agreements and federal funds purchased	201,184	(5,760)	15,974
Proceeds from advances from FHLB	5,477,000	3,965,000	2,665,000
Repayment of advances from FHLB	(5,633,579)	(3,989,167)	(2,560,000)
Retirement of subordinated debt	0	(30,000)	(5,000)
Proceeds from issuance of common stock	1,395	1,200	1,580
Stock tendered for payment of withholding taxes	(760)	(952)	(683)
Repurchase of common stock	0	0	(13,273)
Dividends paid	(39,277)	(25,134)	(23,676)
Net cash used by financing activities	346,339	301,305	393,736
Net increase (decrease) in cash and cash equivalents	(11,019)	(21,625)	61,243
Cash and cash equivalents at beginning of period	112,500	134,125	72,882
Cash and cash equivalents at end of period	101,481	112,500	134,125
Supplemental Disclosures:
Interest payments	60,504	26,377	21,377
Income tax payments	25,664	31,738	22,331
Transfer of Investments Held-to-maturity to Available For Sale Securities	0	0	203,118
Transfer from loans to residential mortgage loans held for sale	60,043	39,744	36,867
Transfers from loans to other real estate owned	$ 289	$ 1,588	$ 637