Equity Securities, Gains (Losses) Measurement Alternative (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Net Gains (Losses) from Measurement Alternative Equity Securities
Total net gains recognized during the period	[1]	$ 622	$ 295	$ 1,436	$ 1,078
Measurement alternative [Member] | Nonmarketable equity securities [Member]
Net Gains (Losses) from Measurement Alternative Equity Securities
Gross unrealized gains due to observable price changes		157	43	342	271
Gross unrealized losses due to observable price changes		(11)	(8)	(11)	(8)
Impairment write-downs		(11)	(5)	(33)	(12)
Realized net gains from sale		102	16	125	91
Total net gains recognized during the period		237	$ 46	423	$ 342
Measurement Alternative Cumulative Gains (Losses)
Cumulative gross unrealized gains due to observable price changes		733		733		$ 415
Cumulative gross unrealized losses due to observable price changes		(36)		(36)		(25)
Cumulative impairment write-downs		$ (52)		$ (52)		$ (33)

[1] (2) Includes OTTI losses of $31 million and $237 million for second quarter 2019 and 2018, respectively, and $67 million and $257 million for the first half of 2019 and 2018, respectively.