Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 29.3	$ 41.6
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	29.0	3.7
Net gain on disposal of premises and equipment	0.1	0.0
Depreciation and amortization	9.7	7.5
Net premium amortization on investment securities	2.4	2.0
Realized and unrealized net gains on mortgage banking activities	(9.1)	(4.7)
Mortgage servicing rights impairment	2.9	0.0
Net gain on sale of investments in unrelated entities	(1.0)	0.0
Net loss (gain) on sale of OREO	(0.6)	(0.4)
Write-downs of OREO and other assets pending disposal	0.0	0.3
Deferred taxes	(4.4)	2.7
Net increase in cash surrender value of company-owned life insurance	(1.5)	(0.7)
Stock-based compensation expense	1.4	1.9
Originations of mortgage loans held for sale	(211.3)	(129.8)
Proceeds from sales of mortgage loans held for sale	224.9	132.7
Changes in operating assets and liabilities, net of effects of acquisition:
Decrease (increase) in interest receivable	0.4	(1.6)
Increase in other assets	(34.9)	(3.7)
(Decrease) increase in accrued interest payable	(1.8)	2.2
Increase (decrease) in accounts payable and accrued expenses	6.0	(6.1)
Net cash provided by operating activities	41.3	47.6
Purchases of investment securities:
Available-for-sale	(419.0)	(161.3)
Proceeds from maturities and pay-downs of investment securities:
Held-to-maturity	22.0	11.3
Available-for-sale	415.5	164.0
Extensions of credit to clients, net of repayments	7.1	(3.2)
Recoveries of loans charged-off	1.5	(1.7)
Proceeds from sale of OREO	1.8	1.8
Proceeds from Sales of Business, Affiliate and Productive Assets	2.2	0.0
Capital expenditures, net of sales	(4.9)	(2.2)
Net cash provided by investing activities	26.2	(12.1)
Cash flows from financing activities:
Net (decrease) increase in deposits	(98.4)	134.0
Net decrease in securities sold under repurchase agreements	(83.5)	(39.8)
Proceeds from issuance of common stock	0.6	0.4
Purchase and retirement of common stock	(32.6)	(2.4)
Dividends paid to common stockholders	(61.2)	(18.7)
Net cash (used in) provided by financing activities	(275.1)	73.5
Net increase in cash and cash equivalents	(207.6)	133.2
Cash and cash equivalents at beginning of period	1,076.8	822.0
Cash and cash equivalents at end of period	869.2	955.2
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	11.5	0.0
Cash paid during the period for interest expense	10.9	12.4
Supplemental disclosures of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	3.2	54.6
Transfer of loans to other real estate owned	0.9	8.4
Capitalization of internally originated mortgage servicing rights	$ 2.0	$ 1.1