Accounting Policies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change	$ (5,012)	$ (6,789)	$ (6,269)	$ (4,972)
Operating lease liability	136	159
Operating lease right-of-use asset	118	139
Deferred rent and lease incentives	$ 18	$ 20
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other liabilities	Other liabilities
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Weighted average common shares adjustment related to stock-based compensation	500,000	500,000	1,100,000
Anti-dilutive potential common shares related to stock-based compensation plans	0	0	0
Maturities of short term investments	3 months
AOCI attributable to parent
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change	$ (119)	$ (1,273)	$ (863)	(48)
Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change	$ (3,478)	$ (4,149)	(4,009)	$ (3,588)
Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change			(7)
Cumulative effect, period of adoption, adjustment | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change			(7)
Accounting Standards Update 2016-13 | Cumulative effect, period of adoption, adjustment | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change			$ (7)