Deferred Policy Acquisition Costs and Value of Business Acquired Level 4 (Details) - USD ($) $ in Millions	1 Months Ended	5 Months Ended	6 Months Ended
	Jun. 30, 2018	May 31, 2018	Jun. 30, 2017	Jun. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 421	$ 405	$ 463
Deferred costs	0	1	1
Amortization — DAC	0	(13)	(28)
Amortization — Unlock benefit (charge), pre-tax	0	(3)	10
Adjustments to unrealized gains and losses on securities AFS and other	0	31	(14)
Balance, end of period	0	421	432
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present Value of Future Insurance Profits, Net	798	0	0	$ 805	$ 0	$ 0
Present Value of Future Insurance Profits, Addition from Acquisition	0	0	0
Present Value of Future Insurance Profits, Amortization Expense	(12)	0	0
Present Value of Future Insurance Profits, Amortization Expense, Assumption Change	5	$ 0	$ 0
Present Value of Future Insurance Profits, Amortization Expense, Next Five Years [Abstract]
Present Value of Future Insurance Profits, Amortization Expense, Year One	28
Present Value of Future Insurance Profits, Amortization Expense, Year Two	63
Present Value of Future Insurance Profits, Amortization Expense, Year Three	59
Present Value of Future Insurance Profits, Amortization Expense, Year Four	54
Present Value of Future Insurance Profits, Amortization Expense, Year Five	$ 51