Condensed Consolidated Statements of Cash Flows $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Cash flows from operating activities:
Net income	$ 63,649	$ 65,688
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation	4,187	2,622
Provision for loan losses	5,031	4,524
Deferred income taxes	4,777	2,822
Net amortization of debt securities	2,009	1,338
Amortization of intangible assets	3,993	1,908
Gain on sale of investment securities	(45)	(9)
Mortgage loans originated for sale	(39,260)	(30,136)
Proceeds from mortgage loans sold	33,503	32,839
Gain on sale of other real estate	(59)	(13)
Gain on state tax credits, net	(469)	(508)
Share-based Payment Arrangement, Noncash Expense	3,016	2,554
Accretion of loan discount	(8,101)	(1,253)
Changes in:
Accrued interest receivable	(1,031)	(5,811)
Accrued interest payable	560	703
Other assets	1,270	(16,309)
Other liabilities	(6,460)	(1,093)
Net cash provided by operating activities	66,570	59,866
Cash flows from investing activities:
Payments for Previous Acquisition	(23,377)	0
Increase in loans	(197,514)	(172,449)
Sale of debt securities, available for sale	314,189	1,451
Paydown or maturity of debt securities, available for sale	95,386	61,881
Paydown or maturity of debt securities, held to maturity	4,760	4,988
Redemption of other investments	43,034	30,593
Sale of state tax credits held for sale	3,978	3,056
Sale of other real estate	4,380	467
Payments for the purchase of:
Available for sale debt securities	(467,695)	(108,121)
Other investments	(61,226)	(44,597)
State tax credits held for sale	(9,666)	(4,704)
Fixed assets, net	(4,008)	(2,369)
Net cash used in investing activities	(297,759)	(229,804)
Cash flows from financing activities:
Net increase (decrease) in noninterest-bearing deposit accounts	25,653	(61,781)
Net increase (decrease) in interest-bearing deposit accounts	(70,446)	115,843
Proceeds from Federal Home Loan Bank advances	1,352,000	1,142,500
Repayments of Federal Home Loan Bank advances	(967,500)	(914,000)
Proceeds from Issuance of Long-term Debt	41,000	0
Repayments of Long-term Debt	(6,286)	0
Net decrease in other borrowings	(58,530)	(91,879)
Cash dividends paid on common stock	(12,055)	(7,866)
Payments for Repurchase of Common Stock	(11,817)	(6,840)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(880)	(3,297)
Net cash provided by financing activities	291,139	172,680
Net increase in cash and cash equivalents	59,950	2,742
Cash and cash equivalents, beginning of period	196,552	153,323
Cash and cash equivalents, end of period	256,502	156,065
Supplemental Cash Flow Information [Abstract]
Cash paid during the period for interest	49,862	31,785
Cash paid during the period for income taxes	12,955	8,492
Noncash transactions:
Transfer to other real estate owned in settlement of loans	$ 7,964	$ 0