Reserve for Unpaid Losses and Loss Adjustment Expenses - GB Additional information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	$ (12)	$ 0
Group Insurance Policy [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development	(321)	(284)
Group Insurance Policy [Member] | Long-term Disability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development	265	195
Group Insurance Policy [Member] | group life term, disability and accident [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development	$ 45	$ 85