Interest and Other Income (Components Of Interest And Other Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest and Other Income [Abstract]
Interest income	$ 7	$ 6
Deferred compensation plan income	4	2
Seismic data sales	3	0
Severance and sales tax refunds	2	3
Other income	2	2
Total interest and other income	$ 18	$ 13