Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Guarantor Obligations [Line Items]
Expires In One Year or Less	$ 947,368
Expires After One Year	65,283
Total Amount Outstanding	1,012,651	[1]	975,968	[1]
Maximum Amount of Future Payments	1,012,651
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	880,712
Expires After One Year	59,497
Total Amount Outstanding	940,209
Maximum Amount of Future Payments	940,209
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	58,475
Expires After One Year	5,786
Total Amount Outstanding	64,261
Maximum Amount of Future Payments	64,261
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires In One Year or Less	8,181
Expires After One Year	0
Total Amount Outstanding	8,181
Maximum Amount of Future Payments	$ 8,181

[1] See below for additional information on our commercial and standby letters of credit.