Transactions with Stockholders (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Schedule of Other Transactions [Line Items]
Advances		$ 71,112,480	$ 69,907,021
Loans And Leases Receivable, Unpaid Principal Balance		9,224,196	8,925,673
Director [Member]
Schedule of Other Transactions [Line Items]
Advances		$ 3,335,000	$ 3,947,000
Federal Home Loan Bank Advances, Percent of Principal	[1]	4.70%	5.60%
Loans And Leases Receivable, Unpaid Principal Balance		$ 112,000	$ 234,000
Federal Home Loan Bank, Mortgage Purchase Program, Unpaid Principal Balance, Percent of Total	[1]	1.20%	2.60%
Regulatory Capital Stock, Value		$ 182,000	$ 166,000
Regulatory Capital Stock, Percent of Total	[1]	4.30%	4.00%

[1] Percentage of total principal (Advances), unpaid principal balance (MPP), and regulatory capital stock.