Parent Company Only Financial Information, Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks	$ 507,187	$ 483,666
Interest-bearing Deposits in Banks and Other Financial Institutions	221,226	199,702
Investment securities available for sale, at fair value	3,948,510	4,043,446
Other assets	460,331	458,920
Total assets	33,647,859	30,483,594
Liabilities and stockholders' equity
Commercial paper	45,423	67,467
Senior notes, at par	550,000	250,000
Subordinated notes, at par	250,000	250,000
Long-term funding capitalized costs	(4,389)	(2,718)
Total long-term funding	3,469,982
Accrued expenses and other liabilities	354,855	318,797
Total liabilities	29,866,971	27,246,151
Preferred equity	256,716	159,929
Common equity	1,752	1,618
Total stockholders’ equity	3,780,888	3,237,443	$ 3,091,312	$ 2,937,246
Total liabilities and stockholders’ equity	33,647,859	30,483,594
Parent Company Only
Assets
Cash and due from banks	16,245	25,544
Interest-bearing Deposits in Banks and Other Financial Institutions	38,374	121,333
Investment securities available for sale, at fair value	0	11,645
Notes and interest receivable from subsidiaries	453,615	301,378
Investments in and receivable due from subsidiaries	3,787,574	3,320,090
Other assets	47,448	51,466
Total assets	4,343,256	3,831,456
Liabilities and stockholders' equity
Commercial paper	45,423	67,467
Senior notes, at par	250,000	250,000
Subordinated notes, at par	250,000	250,000
Long-term funding capitalized costs	(2,043)	(2,718)
Total long-term funding	497,957	497,282
Accrued expenses and other liabilities	18,988	29,264
Total liabilities	562,368	594,013
Preferred equity	256,716	159,929
Common equity	3,524,171	3,077,514
Total stockholders’ equity	3,780,888	3,237,443
Total liabilities and stockholders’ equity	$ 4,343,256	$ 3,831,456