Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets [Abstract]
Cash and due from banks	$ 198,680	$ 185,341
Interest-bearing deposits	104,444	72,554
Investment securities available-for-sale, at fair value	3,183,624	2,925,833
Investment securities held-to-maturity, net	5,477,126	5,293,918
Allowance for credit losses on investment securities held-to-maturity	(309)	0
Investment securities held-to-maturity, net	5,476,817	5,293,918
Federal Home Loan Bank and Federal Reserve Bank stock	94,495	149,046
Loans held for sale (valued under fair value option $46,446 and $35,750)	46,446	36,053
Loans and leases	21,802,517	20,036,986
Allowance for credit losses on loans and leases	(358,522)	(209,096)
Loans and leases, net	21,443,995	19,827,890
Deferred tax assets, net	77,145	61,975
Premises and equipment, net	258,392	270,413
Goodwill	538,373	538,373
Other intangible assets, net	19,994	21,917
Cash surrender value of life insurance policies	557,325	550,651
Accrued interest receivable and other assets	708,887	455,380
Total assets	32,708,617	30,389,344
Liabilities and Equity [Abstract]
Non-interest-bearing	6,193,757	4,446,463
Interest-bearing	20,162,240	18,878,283
Total deposits	26,355,997	23,324,746
Securities sold under agreements to repurchase and other borrowings	1,688,805	1,040,431
Federal Home Loan Bank advances	523,321	1,948,476
Long-term debt	570,029	540,364
Operating lease liabilities	170,731	174,396
Accrued expenses and other liabilities	224,955	153,161
Total liabilities	29,533,838	27,181,574
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock	145,037	145,037
Common stock	937	937
Paid-in capital	1,103,756	1,113,250
Retained earnings	2,024,487	2,061,352
Treasury stock, at cost (3,492,707 and 1,659,749 shares)	(140,883)	(76,734)
Accumulated other comprehensive income (loss), net of tax	41,445	(36,072)
Total shareholders' equity	3,174,779	3,207,770
Total liabilities and shareholders' equity	$ 32,708,617	$ 30,389,344