Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Cash and cash equivalents:
Cash and due from banks	$ 259,775	$ 262,019	$ 225,865
Interest-bearing deposits with banks	1,003,061	426,685	723,726
Total cash and cash equivalents	1,262,836	688,704	949,591
Investment securities:
Securities available for sale, at fair value (Cost of $1,915,461 and allowance for credit losses of $0 for March 31, 2020)	1,971,195	1,956,047	1,466,249
Other investments	62,994	49,124	40,624
Total investment securities	2,034,189	2,005,171	1,506,873
Loans held for sale	71,719	59,363	33,297
Loans:
Total loans - ASU 2016-13	11,506,890
Total loans		11,375,104	11,146,122
Less allowance for loan losses	(144,785)	(61,991)	(56,522)
Loans, net	11,362,105	11,313,113	11,089,600
Other real estate owned	12,844	11,964	11,297
Premises and equipment, net	312,151	317,321	322,553
Bank owned life insurance	233,849	234,567	230,629
Deferred tax assets	46,365	31,316	31,884
Mortgage servicing rights	26,365	30,525	32,415
Core deposit and other intangibles	46,809	49,816	59,619
Goodwill	1,002,900	1,002,900	1,002,900
Other assets	230,779	176,332	136,229
Total assets	16,642,911	15,921,092	15,406,887
Deposits:
Noninterest-bearing	3,367,422	3,245,306	3,219,864
Interest-bearing	8,977,125	8,931,790	8,699,107
Total deposits	12,344,547	12,177,096	11,918,971
Federal funds purchased and securities sold under agreements to repurchase	325,723	298,741	276,891
Other borrowings	1,316,100	815,936	616,250
Other liabilities	335,498	256,306	218,298
Total liabilities	14,321,868	13,548,079	13,030,410
Shareholders' equity:
Common stock - $2.50 par value; authorized 80,000,000 shares; 33,444,236, 33,744,385 and 35,368,521 shares issued and outstanding, respectively	83,611	84,361	88,421
Surplus	1,584,322	1,607,740	1,719,396
Retained earnings	643,345	679,895	582,034
Accumulated other comprehensive income (loss)	9,765	1,017	(13,374)
Total shareholders' equity	2,321,043	2,373,013	2,376,477
Total liabilities and shareholders' equity	16,642,911	15,921,092	15,406,887
Acquired loans
Loans:
Total loans - ASU 2016-13	1,943,971
Total loans		2,117,209	2,830,995
Non-acquired loans
Loans:
Total loans - ASU 2016-13	9,562,919
Total loans		9,252,831	8,310,613
Less allowance for loan losses	$ (144,785)	(56,927)	(52,008)
Loans, net		$ 9,195,904	$ 8,258,605