Commitments and Contingencies (Credit-related Commitments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Loan commitments	$ 4,818,815	$ 5,075,480
Commercial letters of credit and SBLCs	$ 1,632,585	$ 1,655,897

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant