Advances (Credit and Concentration Risk) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018
Advances [Line Items]
Advances Outstanding		$ 65,088		$ 73,495
Interest Income from Advances	[1]	$ 1,659		$ 1,508
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%
MUFG Union Bank, NA
Advances [Line Items]
Advances Outstanding		$ 12,700		$ 16,900
Interest Income from Advances	[1]	371		249
First Republic Bank [Member]
Advances [Line Items]
Advances Outstanding		12,550		8,800
Interest Income from Advances	[1]	248		180
Wells Fargo Financial National Bank West [Member]
Advances [Line Items]
Advances Outstanding	[2]	7,500		5,000
Interest Income from Advances	[1],[2]	191		88
Wells Fargo Bank NA [Member]
Advances [Line Items]
Advances Outstanding	[3]	39		47
Interest Income from Advances	[1],[3]	2		3
Wells Fargo and Company [Member]
Advances [Line Items]
Advances Outstanding		7,539		5,047
Interest Income from Advances		193		91
Bank of the West [Member]
Advances [Line Items]
Advances Outstanding		6,356		6,707
Interest Income from Advances	[1]	155	[2]	150
JPMorgan Chase Bank, National Association
Advances [Line Items]
Advances Outstanding	[3]	5,055		8,359
Interest Income from Advances	[3]	174		216	[1]
Top five borrowers
Advances [Line Items]
Advances Outstanding		44,200		45,813
Interest Income from Advances	[1]	$ 1,141		$ 886
Top five borrowers | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		68.00%		62.00%
Top five borrowers | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		69.00%		59.00%
Top five borrowers | MUFG Union Bank, NA | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		19.00%		23.00%
Top five borrowers | MUFG Union Bank, NA | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		22.00%		17.00%
Top five borrowers | First Republic Bank [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		19.00%		12.00%
Top five borrowers | First Republic Bank [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		15.00%		12.00%
Top five borrowers | Wells Fargo Financial National Bank West [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage	[2]	12.00%		7.00%
Top five borrowers | Wells Fargo Financial National Bank West [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage	[2]	12.00%		6.00%
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%		7.00%
Top five borrowers | Wells Fargo and Company [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		12.00%		6.00%
Top five borrowers | Bank of the West [Member] | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		10.00%		9.00%
Top five borrowers | Bank of the West [Member] | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		9.00%		10.00%
Top five borrowers | JPMorgan Chase Bank, National Association | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage	[3]	8.00%		11.00%
Top five borrowers | JPMorgan Chase Bank, National Association | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage	[3]	11.00%		14.00%
Other Borrowers
Advances [Line Items]
Advances Outstanding		$ 20,888		$ 27,682
Interest Income from Advances	[1]	$ 518		$ 622
Other Borrowers | Percentage of Total Advances Outstanding
Advances [Line Items]
Concentration Risk, Percentage		32.00%		38.00%
Other Borrowers | Percentage of Total Interest Income from Advances
Advances [Line Items]
Concentration Risk, Percentage		31.00%		41.00%

[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.