Fair Value (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)
Fair Value Disclosures [Line Items]
Fair value, assets, level 1 to level 2 transfers, amount	$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers, amount	0	0
Fair value, liabilities, level 1 to level 2 transfers, amount	0	0
Fair value, liabilities, level 2 to level 1 transfers, amount	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 51,000,000	$ 89,000,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | item	71	121
Available-for-sale Securities [Member]
Fair Value Disclosures [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 0
Other Investment Income [Member]
Fair Value Disclosures [Line Items]
Investment Income, Interest and Dividend	$ 7,000,000	$ 7,000,000	$ 8,000,000