Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities:
Net income	$ 367,394	$ 191,786
Adjustments to reconcile net income to net cash provided by (used for) operating activities
Provision for credit losses	(68,562)	213,040
Depreciation, amortization and accretion, net	75,389	71,295
Stock-based compensation expense (benefit)	9,437	(1,023)
Amortization of premium on securities, net	5,188	8,079
Accretion of discount and deferred fees on loans, net	(68,413)	(60,451)
Mortgage servicing rights fair value changes, net	15,685	49,097
Non-designated derivatives fair value changes, net	(378)	(600)
Originations and purchases of mortgage loans held-for-sale	(5,504,906)	(5,653,486)
Early buy-out exercises of mortgage loans held-for-sale guaranteed by U.S. Government Agencies, net of subsequent paydowns or payoffs	(9,747)	(71,625)
Proceeds from sales of mortgage loans held-for-sale	6,014,689	5,280,587
Bank owned life insurance ("BOLI") income	(4,620)	(1,884)
Increase in trading securities, net	(432)	(652)
Increase in brokerage customer receivables, net	(8,942)	(245)
Gains on mortgage loans sold	(178,927)	(260,622)
(Gains) losses on investment securities, net	(8)	3,140
(Gains) losses on sales of premises and equipment, net, and sale of related deposit liabilities	(3,649)	192
Gains on sales and fair value adjustments of other real estate owned, net	(2,134)	(933)
Decrease (increase) in accrued interest receivable and other assets, net	121,657	(154,912)
Decrease in accrued interest payable and other liabilities, net	(27,720)	(33,935)
Net Cash Provided by (Used for) Operating Activities	731,001	(423,152)
Investing Activities:
Proceeds from maturities and calls of available-for-sale securities	1,101,149	1,005,968
Proceeds from maturities and calls of held-to-maturity securities	177,668	698,305
Proceeds from sales of available-for-sale securities	192,227	502,676
Proceeds from sales of equity securities with readily determinable fair value	9,759	6,530
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	2,467	1,691
Purchases of available-for-sale securities	(682,172)	(1,273,798)
Purchases of held-to-maturity securities	(2,537,242)	(125,220)
Purchases of equity securities with readily determinable fair value	(6,000)	(11,367)
Purchases of equity securities without readily determinable fair value	(7,295)	(3,666)
Purchases of Federal Home Loan Bank and Federal Reserve Bank stock, net	180	(34,829)
Contributions to investments in partnerships, net	(2,757)	(606)
Proceeds from sales of other real estate owned	7,263	6,937
Increase in interest-bearing deposits with banks, net	(428,917)	(1,662,172)
Increase in loans, net	(1,169,636)	(5,174,163)
Purchases of premises and equipment, net	(23,434)	(54,392)
Net Cash Used for Investing Activities	(3,366,740)	(6,118,106)
Financing Activities:
Increase in deposit accounts, net	2,863,778	5,737,721
(Decrease) increase in other borrowings, net	(15,716)	91,823
Increase in Federal Home Loan Bank advances, net	12,629	553,500
Proceeds from the issuance of preferred stock, net	0	277,643
Cash payments to settle contingent consideration liabilities recognized in business combinations	(16,583)	(4,523)
Issuance of common shares resulting from the exercise of stock options, employee stock purchase plan and conversion of common stock warrants	14,956	8,023
Common stock repurchases under authorized program	(9,540)	(37,116)
Common stock repurchases for tax withholdings related to stock-based compensation	0	(844)
Dividends paid	(73,960)	(62,750)
Net Cash Provided by Financing Activities	2,775,564	6,563,477
Net Increase in Cash and Cash Equivalents	139,825	22,219
Cash and Cash Equivalents at Beginning of Period	322,474	286,476
Cash and Cash Equivalents at End of Period	$ 462,299	$ 308,695