Variable Interest Entities - Summary of Assets and Liabilities Related to Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions		Sep. 30, 2021		Dec. 31, 2020		Sep. 30, 2020
Variable Interest Entity [Line Items]
Total assets		$ 201,150	[1]	$ 196,434	[1]	$ 200,946
Liabilities	[1]	182,913		178,143
Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		71		89
Liabilities		18		10
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		64		79
Liabilities		16		9
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Total assets		64		79
Low Income Housing Limited Liability Partnership [Member] | Variable interest entities [Member] | Interest, taxes and other liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities		16		9
Venture Debt Financing Entity [Member] | Variable interest entities [Member]
Variable Interest Entity [Line Items]
Total assets		7		10
Liabilities		2		1
Venture Debt Financing Entity [Member] | Variable interest entities [Member] | Loans [Member]
Variable Interest Entity [Line Items]
Total assets		7		10
Venture Debt Financing Entity [Member] | Variable interest entities [Member] | Interest, taxes and other liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities		$ 2		$ 1

[1] Assets