CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Assets [Abstract]
Cash and noninterest-bearing due from banks	$ 167,181,000	$ 137,433,000
Restricted Cash, Current	101,367,000	65,491,000
Interest-bearing due from banks	210,389,000	516,920,000
Federal funds sold and other	6,560,000	1,848,000
Cash and cash equivalents	485,497,000	721,692,000
Securities available-for-sale, at fair value	3,250,006,000	3,083,686,000
Securities held-to-maturity (fair value of $199.0 million and $193.1 million at Mar. 31, 2019 and Dec. 31, 2018, respectively)	194,043,000	194,282,000
Consumer loans held-for-sale	53,658,000	34,196,000
Commercial loans held-for-sale	14,456,000	15,954,000
Loans	18,174,906,000	17,707,549,000
Less allowance for loan losses	(87,194,000)	(83,575,000)
Loans, net	18,087,712,000	17,623,974,000
Premises and equipment, net	262,595,000	265,560,000
Equity method investment	239,861,000	239,237,000
Accrued interest receivable	79,594,000	79,657,000
Goodwill	1,807,121,000	1,807,121,000
Core deposits and other intangible assets	43,850,000	46,161,000
Other real estate owned	15,077,000	15,165,000
Other assets	1,024,388,000	904,359,000
Total assets	25,557,858,000	25,031,044,000
Deposits:
Noninterest-bearing	4,317,787,000	4,309,067,000
Interest-bearing	3,170,570,000	3,464,001,000
Savings and money market accounts	7,349,496,000	7,607,796,000
Time	3,642,608,000	3,468,243,000
Total deposits	18,480,461,000	18,849,107,000
Securities sold under agreements to repurchase	100,698,000	104,741,000
Federal Home Loan Bank advances	2,121,075,000	1,443,589,000
Subordinated debt and other borrowings	484,703,000	485,130,000
Accrued interest payable	26,052,000	23,586,000
Other liabilities	288,930,000	158,951,000
Total liabilities	21,501,919,000	21,065,104,000
Stockholders' equity:
Preferred stock, no par value; 10.0 million shares authorized; no shares issued and outstanding	0	0
Common stock, par value $1.00; 180.0 million shares authorized at Mar. 31, 2019 and Dec. 31, 2018; 77.1 million and 77.5 million shares issued and outstanding at Mar. 31, 2019 and Dec. 31, 2018, respectively	77,064,000	77,484,000
Additional paid-in capital	3,079,358,000	3,107,431,000
Retained earnings	914,545,000	833,130,000
Accumulated other comprehensive loss, net of taxes	(15,028,000)	(52,105,000)
Total stockholders' equity	4,055,939,000	3,965,940,000
Total liabilities and stockholders' equity	$ 25,557,858,000	$ 25,031,044,000