Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Cash and due from banks	$ 198,458,000	$ 185,341,000
Interest-bearing deposits	69,482,000	72,554,000
Investment securities available-for-sale, at fair value	3,016,631,000	2,925,833,000
Investment securities held-to-maturity, net	5,486,206,000	5,293,918,000
Allowance for credit losses on investment securities held-to-maturity	(312,000)	0
Investment securities held-to-maturity, net	5,485,894,000	5,293,918,000
Federal Home Loan Bank and Federal Reserve Bank stock	141,327,000	149,046,000
Loans held for sale (valued under fair value option $22,147 and $35,750)	22,448,000	36,053,000
Loans and leases	20,891,524,000	20,036,986,000
Allowance for credit losses on loans and leases	(334,931,000)	(209,096,000)
Loans and leases, net	20,556,593,000	19,827,890,000
Deferred tax assets, net	80,318,000	61,975,000
Premises and equipment, net	268,420,000	270,413,000
Goodwill	538,373,000	538,373,000
Other intangible assets, net	20,955,000	21,917,000
Cash surrender value of life insurance policies	554,231,000	550,651,000
Accrued interest receivable and other assets	701,744,000	455,380,000
Total assets	31,654,874,000	30,389,344,000
Liabilities and Equity [Abstract]
Non-interest-bearing	4,883,436,000	4,446,463,000
Interest-bearing	19,630,401,000	18,878,283,000
Total deposits	24,513,837,000	23,324,746,000
Securities sold under agreements to repurchase and other borrowings	1,262,749,000	1,040,431,000
Federal Home Loan Bank advances	1,773,399,000	1,948,476,000
Long-term debt	571,212,000	540,364,000
Less: Present value adjustment	177,061,000	174,396,000
Accrued expenses and other liabilities	266,374,000	153,161,000
Total liabilities	$ 28,564,632,000	$ 27,181,574,000
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Series F issued and outstanding (6,000 shares)	6,000	6,000
Preferred Stock, Value, Issued	$ 0.01	$ 0.01
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Issued (93,686,311 shares)	93,686,311
Common Stock, Value, Issued		$ 937,000
Paid-in capital	$ 1,101,324,000	1,113,250,000
Retained earnings	$ 2,009,541,000	$ 2,061,352,000
Treasury stock, at cost (3,514,769 and 1,659,749 shares)	3,514,769	1,659,749
Treasury Stock, Value	$ (141,797,000)	$ (76,734,000)
Accumulated other comprehensive loss, net of tax	(24,800,000)	(36,072,000)
Total shareholders' equity	3,090,242,000	3,207,770,000
Total liabilities and shareholders' equity	$ 31,654,874,000	$ 30,389,344,000
Series F Preferred Stock [Member]
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock, par value (in dollars per share)	$ 145,037,000	$ 145,037,000
Common Stock [Member]
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Value, Issued	$ 937,000