Debt And Lines Of Credit Debt and Lines of Credit (Summary of Long-Term Debt Footnotes) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2007
Debt Instrument [Line Items]
Long-term debt				$ 2,140
Debt Instrument, Fair Value Disclosure		$ 9,900	$ 10,600
Variable Rate [Domain]
Debt Instrument [Line Items]
Debt instrument, interest rate during period		2.90%	2.80%
Long-term debt	[1]	$ 438	$ 271
Municipal Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate during period		5.80%	5.70%
Long-term debt	[2]	$ 594	$ 950
Short-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate during period		2.20%	2.60%
Foreign Corporate Debt Securities [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate during period		2.20%	7.20%
Long-term debt		$ 5	$ 91
Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	[3]	67	275
Interest Rate Swap Unwind [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Deferred gain (loss) on discontinuation of interest rate fair value hedge		$ 8	$ 20

[1] The weighted average interest rate on these notes was 2.9% in 2015 and 2.8% in 2014.

[2] The weighted average interest rate on these bonds was 5.8% in 2015 and 5.7% in 2014.

[3] Includes $8 million at December 31, 2015 and $20 million at December 31, 2014 related to the unamortized gain on interest rate swap unwinds (see Note 14 Derivatives and Hedging Instruments).