Fair Value Measurement and Fair Value of Financial Instruments - Financial Assets Measured at Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Other assets:
Other Assets	$ 9,898		$ 9,898		$ 9,916
Total Gains Losses on Assets	(92)	$ (67)	(139)	$ (119)
Gains Losses on Other Assets			(125)	(52)
Gains Losses On Impaired Loans			(14)	(67)
Fair Value Measurements, Nonrecurring
Fair value measurements
Impaired Financing Receivable, Recorded Investment	78	194	78	194
Other assets:
Other Assets	93	98	93	98
Total	171	292	171	292
Fair Value Measurements, Nonrecurring | Level 1
Other assets:
Total	0	0	0	0
Fair Value Measurements, Nonrecurring | Level 2
Other assets:
Total	0	0	0	0
Fair Value Measurements, Nonrecurring | Level 3
Fair value measurements
Impaired Financing Receivable, Recorded Investment	78	194	78	194
Other assets:
Other Assets	93	98	93	98
Total	171	292	171	292
Loans and Finance Receivables
Other assets:
Total Gains Losses on Assets	2	(58)
Loans and Finance Receivables | Fair Value Measurements, Nonrecurring | Level 1
Fair value measurements
Impaired Financing Receivable, Recorded Investment	0	0	0	0
Loans and Finance Receivables | Fair Value Measurements, Nonrecurring | Level 2
Fair value measurements
Impaired Financing Receivable, Recorded Investment	0	0	0	0
Other Assets
Other assets:
Total Gains Losses on Assets	(94)	(9)
Other Assets | Fair Value Measurements, Nonrecurring | Level 1
Other assets:
Other Assets	0	0	0	0
Other Assets | Fair Value Measurements, Nonrecurring | Level 2
Other assets:
Other Assets	$ 0	$ 0	$ 0	$ 0