Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Guarantor Obligations [Line Items]
Expires In One Year or Less	$ 1,042,109
Expires After One Year	63,508
Total Amount Outstanding	1,105,617	975,968
Maximum Amount of Future Payments	1,105,617
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	972,386
Expires After One Year	55,165
Total Amount Outstanding	1,027,551
Maximum Amount of Future Payments	1,027,551
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	58,678
Expires After One Year	8,343
Total Amount Outstanding	67,021
Maximum Amount of Future Payments	67,021
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	11,045
Expires After One Year	0
Total Amount Outstanding	11,045
Maximum Amount of Future Payments	$ 11,045