Employee Benefit Plans (Changes in Fair Value of Level 3 Pension and Post Retirement Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pooled Separate Accounts | Fixed Maturities | Pension Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	$ 0	$ 38
Actual Return on Assets:
Relating to assets still held at the reporting date		0
Relating to assets sold during the period		0
Purchases, sales and settlements		(38)
Transfers in and/or out of Level 3 (1)		0
Fair Value, end of period		0
Pooled Separate Accounts | Real Estate | Pension Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	760	714
Actual Return on Assets:
Relating to assets still held at the reporting date	39	56
Relating to assets sold during the period	15	8
Purchases, sales and settlements	(44)	(18)
Transfers in and/or out of Level 3 (1)	0	0
Fair Value, end of period	770	760
Corporate Debt | Fixed Maturities | Pension Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	2	1
Actual Return on Assets:
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases, sales and settlements	0	(1)
Transfers in and/or out of Level 3 (1)	(2)	2
Fair Value, end of period	0	2
Corporate Debt | Asset-backed | Fixed Maturities | Other Postretirement Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	1	0
Actual Return on Assets:
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases, sales and settlements	0	(1)
Transfers in and/or out of Level 3 (1)	(1)	2
Fair Value, end of period	0	1
Collateralized Mortgage Obligations | Corporate Debt | Fixed Maturities | Other Postretirement Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	1	2
Actual Return on Assets:
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases, sales and settlements	(1)	(1)
Transfers in and/or out of Level 3 (1)	0	0
Fair Value, end of period	0	1
Collateralized loan obligations | Corporate Debt | Fixed Maturities | Other Postretirement Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	0	2
Actual Return on Assets:
Relating to assets still held at the reporting date		0
Relating to assets sold during the period		0
Purchases, sales and settlements		0
Transfers in and/or out of Level 3 (1)		(2)
Fair Value, end of period		0
Other | Fixed Maturities | Pension Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	62	39
Actual Return on Assets:
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases, sales and settlements	(18)	23
Transfers in and/or out of Level 3 (1)	0	0
Fair Value, end of period	44	62
Other | Fixed Maturities | Other Postretirement Benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	3	5
Actual Return on Assets:
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases, sales and settlements	(2)	(2)
Transfers in and/or out of Level 3 (1)	0	0
Fair Value, end of period	$ 1	$ 3