Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Goodwill, Impairment Loss	$ 6,500		$ 6,500
Goodwill, Gross	8,200		$ 8,200
Amortization of Intangible Assets	19	$ 17
Finite-Lived Intangible Assets, Amortization Expense, 2019	72
Finite-Lived Intangible Assets, Amortization Expense, 2020	71
Finite-Lived Intangible Assets, Amortization Expense, 2021	71
Finite-Lived Intangible Assets, Amortization Expense, 2022	71
Finite-Lived Intangible Assets, Amortization Expense, 2023	70
Optical Communications [Member]
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	$ 1