Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Expires In One Year or Less	$ 2,205,390
Expires After One Year	59,569
Total Amount Outstanding	2,264,959	$ 2,252,016
Maximum Amount of Future Payments	2,264,959
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	2,063,334
Expires After One Year	46,913
Total Amount Outstanding	2,110,247
Maximum Amount of Future Payments	2,110,247
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	116,759
Expires After One Year	8,946
Total Amount Outstanding	125,705
Maximum Amount of Future Payments	125,705
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	25,297
Expires After One Year	3,710
Total Amount Outstanding	29,007
Maximum Amount of Future Payments	$ 29,007