Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Guarantees
Letters of credit	$ 1,806,083	$ 1,796,647
Accrued expenses and other liabilities
Guarantees
Allowance for unfunded credit reserves	14,400	12,400
Other Commitments
Unfunded commitments in investments in qualified affordable housing partnerships, tax credit and other investments	162,100	161,000
Single Family and Multi-family Residential | Loans Sold or Securitized with Recourse | Accrued expenses and other liabilities | Loans Sold or Securitized With Recourse
Guarantees
Allowance for unfunded credit reserves	103	$ 123
Standby Letters of Credit
Guarantees
Letters of credit	1,730,000
Commercial Letters of Credit
Guarantees
Letters of credit	$ 71,400