Variable Interest Entities - Summary of Assets and Liabilities Related to Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions		Sep. 30, 2020		Dec. 31, 2019		Sep. 30, 2019
Variable Interest Entity [Line Items]
Total assets		$ 200,946	[1]	$ 175,375	[1]	$ 184,760
Liabilities	[1]	182,606		157,119
Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		82		98
Liabilities		19		38
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		82		98
Liabilities		18		38
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Total assets		82		98
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member] | Interest, taxes and other liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities		18		38
Venture Debt Financing Entity [Member] | Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		0		0
Liabilities		1		0
Venture Debt Financing Entity [Member] | Variable interest entities [Member] | Interest, taxes and other liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities		$ 1		$ 0

[1] Assets