Commitments, Contingencies and Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Guarantees
Commercial letters of credit and SBLCs	$ 1,655,897	$ 1,525,613
Maximum potential future payments up to recourse component	38,700	46,400
Other Commitments
Unfunded commitments for investments in AHP and other tax credit investments	169,187
Accrued Expenses and Other Liabilities
Guarantees
Allowance for unfunded credit reserves	12,700	15,700
Other Commitments
Unfunded commitments for investments in AHP and other tax credit investments	169,200	174,300
Single Family Residential and Multi-Family Residential | Loans Sold or Securitized with Recourse
Guarantees
Principal amount outstanding on loans sold or securitized	113,700	150,500
Single Family Residential and Multi-Family Residential | Loans Sold or Securitized with Recourse | Accrued Expenses and Other Liabilities
Guarantees
Allowance for unfunded credit reserves	214	$ 373
Standby Letters of Credit
Guarantees
Commercial letters of credit and SBLCs	1,600,000
Commercial Letters Of Credit
Guarantees
Commercial letters of credit and SBLCs	$ 55,700