Intangible Assets and Goodwill (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible asset, amortization expense	$ 37,000,000	$ 37,000,000	$ 45,000,000
Goodwill impairment	$ 0	$ 0	$ 0