Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 38,199	$ 99,736
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Provision for credit losses	76,000	8,600
Deferred Income Tax Expense (Benefit)	(6,518)	9,939
Depreciation, Amortization and Accretion, Net	9,063	9,636
Accretion (Amortization) of Discounts and Premiums, Investments	10,345	10,604
Share-based Payment Arrangement, Noncash Expense	2,609	2,976
Gains (Losses) on Sales of Other Real Estate	(363)	(457)
Gain (Loss) on Disposition of Property Plant Equipment	100	446
Available-for-sale Securities, Gross Realized Gains	(8)	0
Life Insurance, Corporate or Bank Owned, Change in Value	(3,580)	(3,584)
Bank Owned Life Insurance Income	(6)	(64)
Gain (Loss) on Sales of Loans, Net	(2,893)	(764)
Proceeds from Sale of Loans Held-for-sale	75,594	20,613
Payments for Origination of Mortgage Loans Held-for-sale	(59,562)	(33,168)
Increase (Decrease) in Financial Instruments Used in Operating Activities	(2,660)	(654)
Increase (Decrease) in Derivative Assets and Liabilities	(189,718)	(45,896)
Increase (Decrease) in Other Operating Assets	5,447	(23,004)
Increase (Decrease) in Other Accounts Payable and Accrued Liabilities	(13,637)	(11,625)
Net Cash Provided by (Used in) Operating Activities, Total	(61,588)	43,334
Net Cash Provided by (Used in) Investing Activities [Abstract]
Payments to Acquire Debt Securities, Available-for-sale	(122,353)	(126,717)
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale	124,848	81,858
Proceeds from Sale of Available-for-sale Securities	8,963	0
Payments to Acquire Held-to-maturity Securities	(371,935)	(269,670)
Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities	172,032	108,732
Payments for (Proceeds from) Federal Home Loan Bank Stock	7,719	42,612
Payments for (Proceeds from) Other Investing Activities	(2,192)	(700)
Payments for (Proceeds from) Other Loans and Leases	(863,351)	(361,881)
Proceeds of Other Loans and Leases Held-for-investment	390	4,395
Proceeds from Life Insurance Policy	750	2,270
Proceeds from Sale of Foreclosed Assets	2,636	5,561
Payments to Acquire Property, Plant, and Equipment	(3,548)	(5,963)
Net Cash Provided by (Used in) Investing Activities, Total	(1,046,041)	(519,503)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Increase (Decrease) in Deposits	1,188,728	890,903
Proceeds from FHLBank Borrowings, Financing Activities	2,950,000	1,400,000
Payments of FHLBank Borrowings, Financing Activities	(3,125,077)	(2,275,078)
Increase (Decrease) in Federal Funds Purchased and Securities Sold under Agreements to Repurchase, Net	222,318	106,191
Proceeds from Issuance of Senior Long-term Debt	0	300,000
Payments of Debt Issuance Costs	0	(3,642)
Payments of Ordinary Dividends, Common Stock	(36,728)	(30,366)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(1,969)	(1,969)
Proceeds from Stock Options Exercised	118	404
Payments for Repurchase of Common Stock	(76,556)	(13,003)
Payments for Repurchase of Equity, Share-based Compensation	(3,160)	(6,111)
Net Cash Provided by (Used in) Financing Activities, Total	1,117,674	367,329
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	10,045	(108,840)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning Balance	257,895	329,499
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance	267,940	220,659
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activities	50,327	43,372
Income Taxes Paid	4,928	4,274
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Real Estate Owned, Transfer to Real Estate Owned	2,627	3,735
Transfer of Portfolio Loans and Leases to Held-for-sale	214	436
Operating Lease, Right-of-Use Asset	157,786
Less: Present value adjustment	177,061
Liabilities Assumed	0	178,802
Lease Obligation Incurred	$ 0	$ 157,234