Severance Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Severance Costs
Severance costs	$ 1	$ 13	$ 8	$ 23
Severance costs relating to corporate office actions		$ 13		$ 20