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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Loans:
Goodwill	$ 1,764		$ 1,764		$ 1,764
Other assets:
Other Assets	9,814		9,814		$ 10,200
Total Gains Losses on Assets	(67)	$ 2	(119)	$ (18)
Fair Value Measurements, Nonrecurring
Other assets:
Total	292	324	292	324
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
Other assets:
Total	292	324	292	324
Loans and Finance Receivables
Other assets:
Total Gains Losses on Assets	(58)	12	(67)	(3)
Loans and Finance Receivables | Fair Value Measurements, Nonrecurring
Other assets:
Total	194	210	194	210
Loans and Finance Receivables | Fair Value Measurements, Nonrecurring | Level 3
Other assets:
Total	194	210	194	210
Other Assets
Other assets:
Total Gains Losses on Assets	(9)	(10)	(52)	(15)
Other Assets | Fair Value Measurements, Nonrecurring
Other assets:
Total	98	114	98	114
Other Assets | Fair Value Measurements, Nonrecurring | Level 3
Other assets:
Total	$ 98	$ 114	$ 98	$ 114