Advances (Credit Risk Narrative) (Details Textual) $ in Millions	Jun. 30, 2019 USD ($) Institutions	Dec. 31, 2018 USD ($) Institutions
Advances [Abstract]
Number of Top Advances Borrowers | Institutions	10	10
Advances to Ten Largest Borrowers	$ 75,425	$ 80,211
Advances Ten Largest Borrowers Percent of Total	74.70%	74.00%
Allowance for credit losses on advances	$ 0	$ 0
Advances past due	$ 0	$ 0