Investments - Other-than-Temporary Impairments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Investments [Line Items]
Total other-than-temporary impairments	$ 0		$ (2)
Asset-backed securities
Schedule of Investments [Line Items]
Total other-than-temporary impairments	0		0
Corporates
Schedule of Investments [Line Items]
Total other-than-temporary impairments	0		(2)
Other invested assets
Schedule of Investments [Line Items]
Total other-than-temporary impairments	$ 0		$ 0
Predecessor
Schedule of Investments [Line Items]
Total other-than-temporary impairments		$ 0		$ (21)
Predecessor | Asset-backed securities
Schedule of Investments [Line Items]
Total other-than-temporary impairments		0		(1)
Predecessor | Corporates
Schedule of Investments [Line Items]
Total other-than-temporary impairments		0		(20)
Predecessor | Other invested assets
Schedule of Investments [Line Items]
Total other-than-temporary impairments		$ 0		$ 0