Commitments and Contingencies - Small Business Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Carrying amount included in other assets	$ 426,137	$ 262,855
Amount of future funding commitments	250,733	133,946
Permanent and short-term construction loans and letter of credit commitments	204,391	82,786
Funded portion of permanent and short-term loans and letters of credit	104,315	9,528
Letters of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	183,463	190,562
Amounts participated	26,000	30,000
Commitments to fund commercial and industrial loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	9,069,588	8,200,608
Commitments to fund commercial real estate, construction, and land development loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	3,593,171	3,290,041
Commitments under home equity lines of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	1,805,869	1,602,831
Unused credit card lines
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	999,787	1,012,313
Other loan commitments
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	604,353	472,233
Guarantee Obligations
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	16,256,231	14,768,588
Permanent and Short-term Construction Loans and Letter of Credit Commitments
Loss Contingencies [Line Items]
Amounts participated	3,000	1,800
Funded Portion of Permanent and Short-term Loans and Letters of Credit
Loss Contingencies [Line Items]
Amounts participated	$ 3,000	$ 234