Commitments and Contingencies (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring Within One Year		$ 16,994,419	$ 17,029,024
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring After One Year		180,349	479,119
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability		17,174,768	17,508,143
Financial Standby Letter of Credit [Member]
Loss Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring Within One Year		38,275	28,810
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring After One Year		59,440	77,240
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability		97,715	106,050
Forward Contracts [Member] | Mortgages [Member]
Loss Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring Within One Year		264,427	440,849
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring After One Year		0	0
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability		264,427	440,849
Discount Notes [Member]
Loss Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring Within One Year	[1]	43,000	5,500
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Expiring After One Year	[1]	0	0
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	[1]	$ 43,000	$ 5,500

[1] Expiration is based on settlement period rather than underlying contractual maturity of Consolidated Obligations.