Investments - Investments - Commercial Mortgage Loans Credit Quality (Details) $ in Millions	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying Value	$ 3,736	$ 3,704
Commercial Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying Value	$ 3,736	$ 3,704
Avg. Debt-Service Coverage Ratio	2.39	2.49
Commercial Loan [Member] | 65% - 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying Value	$ 481	$ 386
Avg. Debt-Service Coverage Ratio	1.53	1.60
Commercial Loan [Member] | Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying Value	$ 3,255	$ 3,318
Avg. Debt-Service Coverage Ratio	2.52	2.59