Fair Value Measurement and Fair Value of Financial Instruments (Carrying and Fair Value Estimates per the Fair Value Hierarchy of Financial Instruments Measured on a Nonrecurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial assets:
Cash and cash equivalents	$ 3,848,700	$ 3,912,935
Interest-bearing deposits with banks	816,125	736,492
Resale agreements	1,956,822	2,353,503
HTM debt securities	2,997,702	0
Restricted equity securities, at cost	77,682	77,434
Loans held-for-investment, net	42,944,997	41,152,202
Financial liabilities:
FHLB advances	74,619	249,331
Repurchase agreements	300,000	300,000
Carrying Amount
Financial assets:
Cash and cash equivalents	3,848,700	3,912,935
Interest-bearing deposits with banks	816,125	736,492
Resale agreements	1,956,822	2,353,503
HTM debt securities	2,997,702
Restricted equity securities, at cost	77,682	77,434
Loans held-for-sale	631	635
Loans held-for-investment, net	42,944,997	41,152,202
Mortgage servicing rights	5,927	5,706
Accrued interest receivable	155,730	159,833
Financial liabilities:
Demand, checking, savings and money market deposits	46,708,274	45,388,550
Time deposits	8,230,087	7,961,982
FHLB advances	74,619	249,331
Repurchase agreements	300,000	300,000
Long-term debt	147,729	147,658
Accrued interest payable	6,970	11,435
Estimated Fair Value
Financial assets:
Cash and cash equivalents	3,848,700	3,912,935
Interest-bearing deposits with banks	816,125	736,492
Resale agreements	1,906,530	2,335,901
HTM debt securities	2,815,968
Restricted equity securities, at cost	77,682	77,434
Loans held-for-sale	631	635
Loans held-for-investment, net	42,698,185	41,199,599
Mortgage servicing rights	9,853	9,104
Accrued interest receivable	155,730	159,833
Financial liabilities:
Demand, checking, savings and money market deposits	46,708,274	45,388,550
Time deposits	8,202,829	7,966,116
FHLB advances	75,265	250,372
Repurchase agreements	309,225	310,525
Long-term debt	148,298	151,020
Accrued interest payable	6,970	11,435
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	3,848,700	3,912,935
Interest-bearing deposits with banks	0	0
Resale agreements	0	0
HTM debt securities	499,275
Restricted equity securities, at cost	0	0
Loans held-for-sale	0	0
Loans held-for-investment, net	0	0
Mortgage servicing rights	0	0
Accrued interest receivable	0	0
Financial liabilities:
Demand, checking, savings and money market deposits	0	0
Time deposits	0	0
FHLB advances	0	0
Repurchase agreements	0	0
Long-term debt	0	0
Accrued interest payable	0	0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Interest-bearing deposits with banks	816,125	736,492
Resale agreements	1,906,530	2,335,901
HTM debt securities	2,316,693
Restricted equity securities, at cost	77,682	77,434
Loans held-for-sale	631	635
Loans held-for-investment, net	0	0
Mortgage servicing rights	0	0
Accrued interest receivable	155,730	159,833
Financial liabilities:
Demand, checking, savings and money market deposits	46,708,274	45,388,550
Time deposits	8,202,829	7,966,116
FHLB advances	75,265	250,372
Repurchase agreements	309,225	310,525
Long-term debt	148,298	151,020
Accrued interest payable	6,970	11,435
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Interest-bearing deposits with banks	0	0
Resale agreements	0	0
HTM debt securities	0
Restricted equity securities, at cost	0	0
Loans held-for-sale	0	0
Loans held-for-investment, net	42,698,185	41,199,599
Mortgage servicing rights	9,853	9,104
Accrued interest receivable	0	0
Financial liabilities:
Demand, checking, savings and money market deposits	0	0
Time deposits	0	0
FHLB advances	0	0
Repurchase agreements	0	0
Long-term debt	0	0
Accrued interest payable	$ 0	$ 0