Advances (Credit and Concentration Risk) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019		Dec. 31, 2019
Advances [Line Items]
Advances Outstanding		$ 76,888		$ 70,175		$ 65,088
Interest Income from Advances	[1]	$ 319		$ 477
Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		100.00%		100.00%
Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		100.00%		100.00%
First Republic Bank [Member]
Advances [Line Items]
Advances Outstanding		$ 16,250		$ 8,000
Interest Income from Advances	[1]	70		49
MUFG Union Bank, NA [Member]
Advances [Line Items]
Advances Outstanding		10,900		14,550
Interest Income from Advances	[1]	62		103
Wells Fargo Financial National Bank West [Member]
Advances [Line Items]
Advances Outstanding	[2]	9,000		8,000
Interest Income from Advances	[1],[2]	35		47
Wells Fargo Bank NA [Member]
Advances [Line Items]
Advances Outstanding	[3]	36		45
Interest Income from Advances	[1],[3]	1		1
Wells Fargo and Company [Member]
Advances [Line Items]
Advances Outstanding		9,036		8,045
Interest Income from Advances		36		48
Bank of the West [Member]
Advances [Line Items]
Advances Outstanding		8,206		6,807
Interest Income from Advances	[1],[2]	21		43
JPMorgan Chase Bank, National Association
Advances [Line Items]
Advances Outstanding		3,053		8,358
Interest Income from Advances		25	[3]	60	[1]
Top five borrowers
Advances [Line Items]
Advances Outstanding		47,445		45,760
Interest Income from Advances	[1]	$ 214		$ 303
Top five borrowers | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		62.00%		65.00%
Top five borrowers | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		67.00%		64.00%
Top five borrowers | First Republic Bank [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		21.00%		11.00%
Top five borrowers | First Republic Bank [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		22.00%		10.00%
Top five borrowers | MUFG Union Bank, NA [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		14.00%		21.00%
Top five borrowers | MUFG Union Bank, NA [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		19.00%		22.00%
Top five borrowers | Wells Fargo Financial National Bank West [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage	[2]	12.00%		11.00%
Top five borrowers | Wells Fargo Financial National Bank West [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage	[2]	11.00%		10.00%
Top five borrowers | Wells Fargo Bank NA [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage	[3]	0.00%		0.00%
Top five borrowers | Wells Fargo Bank NA [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage	[3]	0.00%		0.00%
Top five borrowers | Wells Fargo and Company [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		12.00%		11.00%
Top five borrowers | Wells Fargo and Company [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		11.00%		10.00%
Top five borrowers | Bank of the West [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		11.00%		10.00%
Top five borrowers | Bank of the West [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		7.00%		9.00%
Top five borrowers | JPMorgan Chase Bank, National Association | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		4.00%	[3]	12.00%
Top five borrowers | JPMorgan Chase Bank, National Association | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		8.00%	[3]	13.00%
Other Borrowers
Advances [Line Items]
Advances Outstanding		$ 29,443		$ 24,415
Interest Income from Advances	[1]	$ 105		$ 174
Other Borrowers | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		38.00%		35.00%
Other Borrowers | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		33.00%		36.00%

[1] Interest income amounts exclude the interest effect of interest rate exchange agreements with derivative counterparties; as a result, the total interest income amounts will not agree to the Statements of Income. The amount of interest income from advances can vary depending on the amount outstanding, terms to maturity, interest rates, and repricing characteristics.

[2] Effective April 15, 2019, Wells Fargo Financial National Bank was renamed Wells Fargo Financial National Bank West.

[3] Nonmember institution.