Guarantees and Indemnifications (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Guarantor Obligations [Line Items]
Guarantees and Indemnifications Outstanding Amount, Expires Within One Year	$ 28,845
Guarantees and Indemnifications Outstanding Amount, Expires After One Year	55,411
Guarantees and Indemnifications, Total Outstanding Amount	84,256
Guarantees and Indemnifications, Maximum Potential Amount of Future Payments	339,403
Financial Standby Letter of Credit
Guarantor Obligations [Line Items]
Guarantees and Indemnifications Outstanding Amount, Expires Within One Year	19,996
Guarantees and Indemnifications Outstanding Amount, Expires After One Year	55,202
Guarantees and Indemnifications, Total Outstanding Amount	75,198
Guarantees and Indemnifications, Maximum Potential Amount of Future Payments	267,174
Performance Guarantee
Guarantor Obligations [Line Items]
Guarantees and Indemnifications Outstanding Amount, Expires Within One Year	5,786
Guarantees and Indemnifications, Total Outstanding Amount	5,786
Guarantees and Indemnifications, Maximum Potential Amount of Future Payments	5,775
Commercial Letters of Credit
Guarantor Obligations [Line Items]
Guarantees and Indemnifications Outstanding Amount, Expires Within One Year	3,063
Guarantees and Indemnifications Outstanding Amount, Expires After One Year	209
Guarantees and Indemnifications, Total Outstanding Amount	3,272
Guarantees and Indemnifications, Maximum Potential Amount of Future Payments	$ 66,454