Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Guarantor Obligations [Line Items]
Expires in One Year or Less	$ 2,963,742
Expires After One Year	99,668
Total Amount Outstanding	3,063,410	$ 3,007,118
Maximum Amount of Future Payments	3,063,410
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	2,833,713
Expires After One Year	79,552
Total Amount Outstanding	2,913,265
Maximum Amount of Future Payments	2,913,265
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	118,222
Expires After One Year	20,116
Total Amount Outstanding	138,338
Maximum Amount of Future Payments	138,338
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	11,807
Expires After One Year	0
Total Amount Outstanding	11,807
Maximum Amount of Future Payments	$ 11,807