Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 30.7	$ 93.9
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for (reversal of) credit losses	59.6	(5.1)
Net gain on disposal of premises and equipment	(1.4)	(0.4)
Depreciation and amortization	27.5	22.3
Net premium amortization on investment securities	13.5	18.3
Net loss on investment securities transactions	0.2	0.1
Realized and unrealized net gains on mortgage banking activities	(7.6)	(10.7)
Net gain on sale of OREO	(0.1)	(0.2)
Gain (Loss) on Extinguishment of Debt	(1.4)	0.0
Mortgage servicing rights recovery	(3.4)	(5.9)
Deferred taxes	(8.8)	9.0
Net increase in cash surrender value of company-owned life insurance	(4.7)	(2.6)
Stock-based compensation expense	6.2	5.5
Originations of mortgage loans held for sale	(241.2)	(359.3)
Proceeds from sales of mortgage loans held for sale	263.1	394.3
Changes in operating assets and liabilities:
(Increase) decrease in interest receivable	(10.1)	0.2
Decrease (increase) in other assets	7.6	(39.3)
Decrease in accrued interest payable	(1.8)	(0.8)
Increase (decrease) in accounts payable and accrued expenses	141.3	(13.2)
Net cash provided by operating activities	269.2	106.1
Purchases of investment securities:
Held-to-maturity	(848.2)	(1,022.1)
Available-for-sale	(2,521.2)	(1,219.9)
Proceeds from sales, maturities, and pay-downs of investment securities:
Held-to-maturity	193.4	55.4
Available-for-sale	1,057.8	542.5
Extensions of credit to clients, net of repayments	(39.2)	(37.0)
Recoveries of loans charged-off	0.0	(5.7)
Proceeds from sale of OREO	1.2	1.0
Proceeds from the sale of Health Savings Accounts	1.4	0.0
Acquisition of bank and bank holding company, net of cash and cash equivalents received	2,006.9	0.0
Payments for (Proceeds from) Productive Assets	(15.5)	(0.3)
Net cash used in investing activities	(163.4)	(1,674.7)
Cash flows from financing activities:
Net (decrease) increase in deposits	(1,093.8)	1,348.7
Net increase (decrease) in securities sold under repurchase agreements	8.5	(52.7)
Repayments of long-term debt	(157.9)	0.0
Advances on long-term debt	8.0	0.0
Payments of Stock Issuance Costs	(0.8)	0.0
Proceeds from issuance of common stock, net	0.1	0.4
Purchase and retirement of common stock	(65.9)	(5.4)
Dividends paid to common stockholders	(89.5)	(50.8)
Net cash (used in) provided by financing activities	(1,391.3)	1,240.2
Net decrease in cash and cash equivalents	(1,285.5)	(328.4)
Cash and cash equivalents at beginning of period	2,344.8	2,276.8
Cash and cash equivalents at end of period	1,059.3	1,948.4
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	13.8	35.7
Cash paid during the period for interest expense	13.5	9.8
Supplemental disclosures of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	19.9	0.4
Net change in unamortized (losses) gains on available-for-sale securities transferred into held-to-maturity	10.9	0.0
Debt Securities, Available-For-Sale, Transfer, Unrealized Gain (Loss)	463.6	672.2
Transfer of loans from held-for-sale to held for investment	19.8	0.0
Transfer of loans to other real estate owned	0.1	0.3
Asset Acquisition, Consideration Transferred, Equity Interest Issued and Issuable	1,723.3	0.0
Capitalization of internally originated mortgage servicing rights	1.6	0.9
Investment securities	2,699.0	0.0
Securities Purchased under Agreements to Resell, Increase	101.1	0.0
Loans held for sale	217.0	0.0
Loans held for investment, net	7,645.5	0.0
Premises and equipment	144.9	0.0
Goodwill	478.2	0.0
Company-owned life insurance	186.6	0.0
Noncash or Part Noncash Acquisition, Deferred Tax Assets Acquired	63.6	0.0
Noncash or Part Noncash Acquisition, Intangible Assets Acquired, Other Real Estate Owned	15.8	0.0
Other assets	198.0	0.0
Total noncash assets acquired	11,823.9	0.0
Noncash or Part Noncash Acquisition, Liabilities Assumed, Deposits	11,688.0	0.0
Securities sold under repurchase agreements	74.0	0.0
Accounts payable and accrued expenses	110.1	0.0
Long-term debt	159.3	0.0
Noncash or Part Noncash Acquisition, Liabilities Assumed, Trust preferred securities	76.1	0.0
Total liabilities assumed	12,107.5	0.0
Core Deposits
Supplemental disclosures of non-cash investing and financing activities:
Other intangibles	72.9	0.0
Servicing Contracts
Supplemental disclosures of non-cash investing and financing activities:
Other intangibles	$ 1.3	$ 0.0