Fair Value Measurement and Fair Value of Financial Instruments (Carrying and Fair Values Estimates per the Fair Value Hierarchy of Financial Instruments on a nonrecurring basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financial assets:
Cash and cash equivalents	$ 3,912,935	$ 4,017,971
Interest-bearing deposits with banks	736,492	809,728
Resale agreements	2,353,503	1,460,000
Restricted equity securities, at cost	77,434	83,046
Loans held-for-investment, net	41,152,202	37,770,972
Financial liabilities:
Time deposits	7,961,982
FHLB advances	249,331	652,612
Repurchase agreements	300,000	300,000
Carrying Amount
Financial assets:
Cash and cash equivalents	3,912,935	4,017,971
Interest-bearing deposits with banks	736,492	809,728
Resale agreements	2,353,503	1,460,000
Restricted equity securities, at cost	77,434	83,046
Loans held-for-sale	635	1,788
Loans held-for-investment, net	41,152,202	37,770,972
Mortgage servicing rights	5,706	5,522
Accrued interest receivable	159,833	150,140
Financial liabilities:
Demand, checking, savings and money market deposits	45,388,550	35,862,403
Time deposits	7,961,982	9,000,349
Short-term borrowings		21,009
FHLB advances	249,331	652,612
Repurchase agreements	300,000	300,000
Long-term debt	147,658	147,376
Accrued interest payable	11,435	11,956
Estimated Fair Value
Financial assets:
Cash and cash equivalents	3,912,935	4,017,971
Interest-bearing deposits with banks	736,492	809,728
Resale agreements	2,335,901	1,464,635
Restricted equity securities, at cost	77,434	83,046
Loans held-for-sale	635	1,788
Loans held-for-investment, net	41,199,599	37,803,940
Mortgage servicing rights	9,104	8,435
Accrued interest receivable	159,833	150,140
Financial liabilities:
Demand, checking, savings and money market deposits	45,388,550	35,862,403
Time deposits	7,966,116	9,016,884
Short-term borrowings		21,009
FHLB advances	250,372	659,631
Repurchase agreements	310,525	317,850
Long-term debt	151,020	150,131
Accrued interest payable	11,435	11,956
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	3,912,935	4,017,971
Interest-bearing deposits with banks	0	0
Resale agreements	0	0
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
Short-term borrowings		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	736,492	809,728
Resale agreements	2,335,901	1,464,635
Restricted equity securities, at cost	77,434	83,046
Loans held-for-sale	635	1,788
Loans held-for-investment, net	0	0
Mortgage servicing rights	0	0
Accrued interest receivable	159,833	150,140
Financial liabilities:
Demand, checking, savings and money market deposits	45,388,550	35,862,403
Time deposits	7,966,116	9,016,884
Short-term borrowings		21,009
FHLB advances	250,372	659,631
Repurchase agreements	310,525	317,850
Long-term debt	151,020	150,131
Accrued interest payable	11,435	11,956
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
Restricted equity securities, at cost	0	0
Loans held-for-sale	0	0
Loans held-for-investment, net	41,199,599	37,803,940
Mortgage servicing rights	9,104	8,435
Accrued interest receivable	0	0
Financial liabilities:
Demand, checking, savings and money market deposits	0	0
Time deposits	0	0
Short-term borrowings		0
FHLB advances	0	0
Repurchase agreements	0	0
Long-term debt	0	0
Accrued interest payable	$ 0	$ 0