Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 454	$ 407
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	(12)	9
Total realized and unrealized investment gains (losses)	(10)	18
Purchases	279	126
Sales	(77)	(68)
Settlements	(74)	(102)
Transfers into Level 3	77	169
Transfers out of Level 3	(212)	(96)
Balance, Ending, Assets	437	454
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	(4)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	(9)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	98	130
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	(4)	3
Total realized and unrealized investment gains (losses)	(5)	3
Purchases	117	18
Sales	(5)	(5)
Settlements	(9)	(54)
Transfers into Level 3	35	16
Transfers out of Level 3	(9)	(10)
Balance, Ending, Assets	222	98
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	(5)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1	1
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	0	0
Total realized and unrealized investment gains (losses)	0	0
Purchases	0	0
Sales	0	0
Settlements	(1)	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	0	1
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	335	199
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	(8)	3
Total realized and unrealized investment gains (losses)	(3)	5
Purchases	162	107
Sales	(72)	0
Settlements	(64)	(43)
Transfers into Level 3	42	153
Transfers out of Level 3	(203)	(86)
Balance, Ending, Assets	197	335
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	(2)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	(4)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	20	19
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	0	3
Total realized and unrealized investment gains (losses)	(2)	3
Purchases	0	1
Sales	0	(3)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	18	20
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	(2)
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Derivative financial instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	0	0
Reported in Net investment income	0
Total realized and unrealized investment gains (losses)	0	0
Total realized and unrealized investment gains (losses)	0	1
Purchases	0	0
Sales	0	(1)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	0	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Net income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2018 recognized in Other comprehensive income (loss)	0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Life settlement contracts, included in Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	0	58
Total realized and unrealized investment gains (losses)		0
Total realized and unrealized investment gains (losses)		6
Purchases		0
Sales		(59)
Settlements		(5)
Transfers into Level 3		0
Transfers out of Level 3		0
Balance, Ending, Assets		0
Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2017 recognized in Net income (loss)		0
Reported in Net realized investment gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	2	3
Reported in Net realized investment gains (losses) | Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	(1)	0
Reported in Net realized investment gains (losses) | States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	0	0
Reported in Net realized investment gains (losses) | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	5	2
Reported in Net realized investment gains (losses) | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	(2)	0
Reported in Net realized investment gains (losses) | Derivative financial instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)	$ 0	1
Reported in Net realized investment gains (losses) | Life settlement contracts, included in Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		6
Reported in Other revenues | Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues | States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues | Derivative financial instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		0
Reported in Other revenues | Life settlement contracts, included in Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Other comprehensive income (loss)		$ 6