Consolidated Statements of Cash Flows - (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities:
Net income	$ 130.4	$ 114.6
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Provision for credit losses	33.5	5.6
Depreciation and amortization of premises and equipment	11.2	9.5
Amortization of other acquisition-related intangible assets	10.7	6.7
Expense related to operating leases	9.8	9.4
Expense related to share-based awards	7.1	6.2
ESOP common stock committed to be released	1.2	1.4
Net gains on sales of loans	(15.5)	(0.4)
Net losses on sales of residential mortgage loans	(0.7)	(0.2)
Originations of loans held-for-sale	(48.7)	(23.5)
Proceeds from sales of loans held-for-sale	540.6	35.4
Net decrease in trading debt securities	7.1	0.1
Excess income tax benefits from stock option exercises	0.0	0.3
Net changes in other assets and other liabilities	(470.9)	(186.6)
Net cash provided by (used in) operating activities	215.8	(21.5)
Cash Flows from Investing Activities:
Proceeds from sales of equity securities	0.7	0.2
Proceeds from principal repayments and maturities of debt securities available-for-sale	207.9	105.8
Proceeds from sales of debt securities available-for-sale	0.1	170.4
Proceeds from principal repayments and maturities of debt securities held-to-maturity	94.8	33.0
Purchases of debt securities available-for-sale	(822.8)	(184.4)
Purchases of debt securities held-to-maturity	(87.3)	(59.1)
Net purchases of Federal Reserve Bank stock	(24.0)	(15.0)
Net (purchases) redemptions of Federal Home Loan Bank stock	(42.2)	42.8
Proceeds from sales of loans	27.8	14.8
Net principal disbursements of loans	(624.9)	(274.7)
Purchases of loans	(8.5)	(15.8)
Purchases of premises and equipment	(7.8)	(1.9)
Purchases of leased equipment, net	(3.8)	(2.4)
Proceeds from sales of real estate owned	3.3	5.6
Return of premium on bank-owned life insurance, net	0.0	0.5
Net cash paid in acquisitions	0.0	(60.0)
Net cash used in investing activities	(1,286.7)	(240.2)
Cash Flows from Financing Activities:
Net increase in deposits	1,151.6	741.9
Net increase (decrease) in borrowings with terms of three months or less	766.2	(702.5)
Repayments of borrowings with terms of more than three months	(10.1)	(31.7)
Cash dividends paid on common stock	(77.3)	(65.2)
Cash dividends paid on preferred stock	(3.5)	(3.5)
Repurchases of common stock	(305.8)	(1.7)
Proceeds from stock options exercised	0.7	6.9
Net cash provided by (used in) financing activities	1,521.8	(55.8)
Net increase (decrease) in cash and cash equivalents	450.9	(317.5)
Cash and cash equivalents at beginning of period	801.0	932.0
Cash and cash equivalents at end of period	1,251.9	614.5
Supplemental Information:
Interest payments	105.4	107.0
Income taxes payments	13.2	9.1
Significant non-cash transactions:
Right-of-use assets obtained in exchange for lessee operating lease liabilities	14.3	10.3
Unsettled purchases of securities	7.5	14.6
Real estate properties acquired by foreclosure	$ 1.6	$ 2.9