Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Offsetting Assets [Abstract]
Securities Purchased under Agreements to Resell, Gross	$ 2,600	$ 200
Securities Purchased under Agreements to Resell, Liability	0	0
Securities Purchased under Agreements to Resell	2,600	200
Securities Purchased under Agreements to Resell, Financial Instruments, Not Offset	0	0
Securities Purchased under Agreements to Resell, Collateral Received, Not Offset	(2,600)	(200)
Securities Purchased under Agreements to Resell, Amount Offset Against Collateral	0	0
Securities Borrowed, Gross	634	1,116
Securities Borrowed, Liability	0	0
Securities Borrowed	634	1,116
Securities Borrowed, Financial Instruments, Not Offset	(171)	(83)
Securities Borrowed, Collateral Received, Not Offset	(437)	(1,003)
Securities Borrowed, Net	26	30
Total, Gross	3,234	1,316
Total, Liability	0	0
Total	3,234	1,316
Total, Financial Instruments, Not Offset	(171)	(83)
Total, Collateral Received, Not Offset	(3,037)	(1,203)
Total, Net	26	30
Offsetting Liabilities [Abstract]
Securities Loaned, Gross	1,409	838
Securities Loaned, Asset	0	0
Securities Loaned	1,409	838
Securities Loaned, Financial Instruments, Not Offset	(171)	(83)
Securities Loaned, Collateral Pledged, Not Offset	(1,112)	(699)
Securities Loaned, Net	126	56
Offsetting Assets [Line Items]
Securities Purchased under Agreements to Resell, Fair Value of Collateral	2,600	206
Exchange Cleared [Member]
Offsetting Assets [Line Items]
Cash Collateral Paid for Securities Borrowed, at Carrying Value	175	757
Cash Collateral Received for Securities Loaned, at Carrying Value	$ 784	$ 401