Fair Value of Financial Instruments (Redemption Of The Plan's Level 3 Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
MS IFHF SVP LP Cayman [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidation Period (in years)	5 years
MS IFHF SVP LP Alpha [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidation Period (in years)	5 years
RII World Timberfund, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidation Period (in years)	10 years
Interest in Limited Partnerships and Limited Liability Companies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 115	$ 118	$ 92
Interest in Limited Partnerships and Limited Liability Companies [Member] | MS IFHF SVP LP Cayman [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1
Interest in Limited Partnerships and Limited Liability Companies [Member] | MS IFHF SVP LP Alpha [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1
Interest in Limited Partnerships and Limited Liability Companies [Member] | RII World Timberfund, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5
Interest in Limited Partnerships and Limited Liability Companies [Member] | E Casino Road, LLC (member)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 15
Capitalization Rate	7.00%
Interest in Limited Partnerships and Limited Liability Companies [Member] | Comm Drive, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 9
Capitalization Rate	8.00%
Interest in Limited Partnerships and Limited Liability Companies [Member] | CTE Drive, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 10
Capitalization Rate	9.50%
Interest in Limited Partnerships and Limited Liability Companies [Member] | Oakbrook Parkway LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 26
Capitalization Rate	7.75%
Interest in Limited Partnerships and Limited Liability Companies [Member] | West Jefferson, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 26
Capitalization Rate	8.75%
Interest in Limited Partnerships and Limited Liability Companies [Member] | MacCorkle Ave SE, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 14
Capitalization Rate	8.50%
Interest in Limited Partnerships and Limited Liability Companies [Member] | S Pike Road West, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1
Capitalization Rate	8.50%
Interest in Limited Partnerships and Limited Liability Companies [Member] | N US 131, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1
Capitalization Rate	9.50%
Interest in Limited Partnerships and Limited Liability Companies [Member] | E Stockton Blvd, LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 6
Capitalization Rate	7.50%