Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Expires In One Year or Less	$ 2,430,853
Expires After One Year	118,767
Total Amount Outstanding	2,549,620	$ 2,252,016
Maximum Amount of Future Payments	2,549,620
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	2,290,762
Expires After One Year	95,663
Total Amount Outstanding	2,386,425
Maximum Amount of Future Payments	2,386,425
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	125,310
Expires After One Year	22,804
Total Amount Outstanding	148,114
Maximum Amount of Future Payments	148,114
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	14,781
Expires After One Year	300
Total Amount Outstanding	15,081
Maximum Amount of Future Payments	$ 15,081