Fair Value Disclosures Fair Value Difference Between Fair Value and Remaining Contractual Principal Balance Outstanding (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ (6,397)	$ (19,290)	$ (12,458)	$ (32,947)
Federal Home Loan Bank, Advances, Par Value	[1]	15,000		15,000		$ 15,000
Advances, Fair Value Disclosure	[1]	15,063		15,063		15,093
Federal Home Loan Bank, Advances, Valuation Adjustments under Fair Value Option	[1]	63		63		93
Consolidated Obligation Bonds [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Aggregate Unpaid Principal Balance		5,629,265		5,629,265		7,926,000
Aggregate Fair Value		5,605,291		5,605,291		7,895,510
Fair value option valuation adjustment and accrued interest		$ (23,974)		$ (23,974)		$ (30,490)

[1] At June 30, 2017 and December 31, 2016, none of the Advances were 90 days or more past due or had been placed on non-accrual status.