Basis of Presentation Basis of Presentation (Out-of-period-correction) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Income (Loss) [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year	$ 12
DAC [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year	8
Benefits, Claims, Losses and Settlement Expenses [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year	4
Income Tax Provision [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year	20
LTC [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year		$ 29
Net cash provided by (used in) operating activities [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Correction of prior period cash flows	(178)	(22)
Net cash provided by (used in) investing activities [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Correction of prior period cash flows	28	22
Cash and Cash Equivalents [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Correction of prior period cash flows	150	$ 150
Out of period corrections in current year			$ 150
Other Comprehensive Income (Loss) [Member] | Decrease to other comprehensive income related to deferred taxes on currency translation adjustments [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Out of period corrections in current year	$ 87