Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Expires In One Year or Less	$ 2,770,284
Expires After One Year	77,392
Total Amount Outstanding	2,847,676	$ 2,252,016
Maximum Amount of Future Payments	2,847,676
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	2,571,352
Expires After One Year	58,290
Total Amount Outstanding	2,629,642
Maximum Amount of Future Payments	2,629,642
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	119,666
Expires After One Year	19,102
Total Amount Outstanding	138,768
Maximum Amount of Future Payments	138,768
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	79,266
Expires After One Year	0
Total Amount Outstanding	79,266
Maximum Amount of Future Payments	$ 79,266