Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Offsetting Assets [Abstract]
Securities Purchased under Agreements to Resell, Gross	$ 200
Securities Purchased under Agreements to Resell, Liability	0
Securities Purchased under Agreements to Resell	200
Securities Purchased under Agreements to Resell, Financial Instruments, Not Offset	0
Securities Purchased under Agreements to Resell, Collateral Received, Not Offset	(200)
Securities Purchased under Agreements to Resell, Amount Offset Against Collateral	0
Securities Borrowed, Gross	1,116	$ 176
Securities Borrowed, Liability	0	0
Securities Borrowed	1,116	176
Securities Borrowed, Financial Instruments, Not Offset	(83)	(104)
Securities Borrowed, Collateral Received, Not Offset	(1,003)	(61)
Securities Borrowed, Net	30	11
Total, Gross	1,316
Total, Liability	0
Total	1,316
Total, Financial Instruments, Not Offset	(83)
Total, Collateral Received, Not Offset	(1,203)
Total, Net	30
Offsetting Liabilities [Abstract]
Securities Loaned, Gross	838	887
Securities Loaned, Asset	0	0
Securities Loaned	838	887
Securities Loaned, Financial Instruments, Not Offset	(83)	(104)
Securities Loaned, Collateral Pledged, Not Offset	(699)	(700)
Securities Loaned, Net	56	83
Offsetting Assets [Line Items]
Securities Purchased under Agreements to Resell, Fair Value of Collateral	206
Cash Collateral Paid for Securities Borrowed, at Carrying Value	1,003	140
Cash Collateral Received for Securities Loaned, at Carrying Value	838	887
Exchange Cleared [Member]
Offsetting Assets [Line Items]
Cash Collateral Paid for Securities Borrowed, at Carrying Value	757	65
Cash Collateral Received for Securities Loaned, at Carrying Value	$ 401	$ 543