Investments - Recorded Investment in CMLs by LTV and DSC Ratio Categories (Details) - Commercial Portfolio Segment $ in Millions	Jun. 30, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 576
% of Total	100.00%
Fair Value
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 583
% of Total	100.00%
Greater than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 550
Greater than 1.00 but less than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	26
Less than 50%
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 441
% of Total	77.00%
Less than 50% | Fair Value
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 447
% of Total	77.00%
Less than 50% | Greater than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 415
Less than 50% | Greater than 1.00 but less than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	26
LTV 50 to 60 Percent
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 102
% of Total	18.00%
LTV 50 to 60 Percent | Fair Value
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 103
% of Total	18.00%
LTV 50 to 60 Percent | Greater than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 102
LTV 50 to 60 Percent | Greater than 1.00 but less than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	0
LTV 60 to 75 Percent
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 33
% of Total	5.00%
LTV 60 to 75 Percent | Fair Value
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 33
% of Total	5.00%
LTV 60 to 75 Percent | Greater than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 33
LTV 60 to 75 Percent | Greater than 1.00 but less than 1.25
Debt Securities, Available-for-sale [Line Items]
Unpaid Principal Balance	$ 0