Comprehensive Loss (Narrative) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Apr. 01, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Discount rate - used at year end to value obligation (in hundredths)	3.70%	4.10%	4.00%	4.50%
Other comprehensive income (loss) before reclassifications		$ 105
Pension Settlement Cost [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications, pretax	$ (83)
Reclassifications, net of tax	$ (51)