Fair Value Measurements - Changes in balances of Level 3 financial liabilities carried at fair value (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		$ (2,776)	$ (2,129)	$ (2,542)		$ (1,759)
Total realized/unrealized gains (losses) included in Net income		(223)	(127)	(286)		(386)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0		0
Purchases and issuances		(151)	(65)	(395)		(224)
Sales and settlements		45	28	118		76
Transfer into Level 3		0	0	0		0
Transfer out of Level 3		0	0	0		0
Financial liabilities, Ending Balance	[1],[2]	(3,105)	(2,293)	(3,105)		(2,293)
Embedded derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		(2,776)	(2,129)	(2,542)		(1,759)
Total realized/unrealized gains (losses) included in Net income		(223)	(127)	(286)	[3]	(386)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0		0
Purchases and issuances		(151)	(65)	(395)		(224)
Sales and settlements		45	28	118		76
Transfer into Level 3		0	0	0		0
Transfer out of Level 3		0	0	0		0
Financial liabilities, Ending Balance		$ (3,105)	$ (2,293)	$ (3,105)		$ (2,293)

[1] As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets.

[2] As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets.

[3] Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $44 million in the first nine months of 2018.