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	Sep. 30, 2023	Dec. 31, 2022
Financial assets:
Cash and cash equivalents	$ 4,561,178	$ 3,481,784
Interest-bearing deposits with banks	17,213	139,021
Resale agreements	785,000	792,192
HTM debt securities	2,964,235	3,001,868
Restricted equity securities, at cost	79,522	78,624
Financial liabilities:
Repurchase agreements	0	300,000
Carrying Amount
Financial assets:
Cash and cash equivalents	4,561,178	3,481,784
Interest-bearing deposits with banks	17,213	139,021
Resale agreements	785,000	792,192
HTM debt securities	2,964,235	3,001,868
Restricted equity securities, at cost	79,522	78,624
Loans held-for-sale	4,762	25,644
Loans held-for-investment, net	50,251,661	47,606,785
Mortgage servicing rights	5,208	6,235
Accrued interest receivable	317,881	263,430
Financial liabilities:
Demand, checking, savings and money market deposits	38,435,954	42,637,316
Time deposits	16,651,077	13,330,533
Repurchase agreements		300,000
Short-term borrowings	4,500,000
Long-term debt	148,173	147,950
Accrued interest payable	150,890	37,198
Estimated Fair Value
Financial assets:
Cash and cash equivalents	4,561,178	3,481,784
Interest-bearing deposits with banks	17,213	139,021
Resale agreements	672,250	693,656
HTM debt securities	2,308,048	2,455,171
Restricted equity securities, at cost	79,522	78,624
Loans held-for-sale	4,762	25,644
Loans held-for-investment, net	48,992,846	46,670,690
Mortgage servicing rights	9,821	10,917
Accrued interest receivable	317,881	263,430
Financial liabilities:
Demand, checking, savings and money market deposits	38,435,954	42,637,316
Time deposits	16,547,883	13,228,777
Repurchase agreements		304,097
Short-term borrowings	4,500,000
Long-term debt	144,214	143,483
Accrued interest payable	150,890	37,198
Estimated Fair Value | Level 1
Financial assets:
Cash and cash equivalents	4,561,178	3,481,784
Interest-bearing deposits with banks	0	0
Resale agreements	0	0
HTM debt securities	470,618	471,469
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
Repurchase agreements		0
Short-term borrowings	0
Long-term debt	0	0
Accrued interest payable	0	0
Estimated Fair Value | Level 2
Financial assets:
Cash and cash equivalents	0	0
Interest-bearing deposits with banks	17,213	139,021
Resale agreements	672,250	693,656
HTM debt securities	1,837,430	1,983,702
Restricted equity securities, at cost	79,522	78,624
Loans held-for-sale	4,762	25,644
Loans held-for-investment, net	0	0
Mortgage servicing rights	0	0
Accrued interest receivable	317,881	263,430
Financial liabilities:
Demand, checking, savings and money market deposits	38,435,954	42,637,316
Time deposits	16,547,883	13,228,777
Repurchase agreements		304,097
Short-term borrowings	4,500,000
Long-term debt	144,214	143,483
Accrued interest payable	150,890	37,198
Estimated Fair Value | 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	0
Restricted equity securities, at cost	0	0
Loans held-for-sale	0	0
Loans held-for-investment, net	48,992,846	46,670,690
Mortgage servicing rights	9,821	10,917
Accrued interest receivable	0	0
Financial liabilities:
Demand, checking, savings and money market deposits	0	0
Time deposits	0	0
Repurchase agreements		0
Short-term borrowings	0
Long-term debt	0	0
Accrued interest payable	$ 0	$ 0