Note 8. Short And Long-Term Debt Other Debt Facilities (Details) - USD ($) $ in Millions	1 Months Ended
	Aug. 31, 2015	Dec. 31, 2015	Oct. 23, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Letter of credit borrowing capacity		$ 125	$ 125
Outstanding letter of credit		134
Unsecured Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Increase in borrowing capacity	$ 7
Letter of credit borrowing capacity		88		$ 81
Outstanding letter of credit		81
June 2017 [Member] \| Unsecured Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Letter of credit borrowing capacity		81
September 2018 [Member] \| Unsecured Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Letter of credit borrowing capacity		$ 7