Description of Company And Significant Accounting Policies (Narrative) (Details)		3 Months Ended
	Jan. 01, 2019 USD ($)	Mar. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Jan. 01, 2018 USD ($)
Accounting Policies [Abstract]
Number of reportable segments | segment		5
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Amount reclassified from cost of revenues to selling, general and administrative expense	$ 34,000,000
Operating lease right-of-use asset	185,000,000	$ 180,000,000	$ 0
Operating lease, liability		247,000,000
Equity in and advances to unconsolidated affiliates		810,000,000	744,000,000
Cumulative effect of change in accounting policy	21,000,000			$ 144,000,000
Deferred rent		$ 92,000,000
Accounting Standards Update 2016-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating lease right-of-use asset			$ 185,000,000
Operating lease, liability	253,000,000
Deferred rent	(68,000,000)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Equity in and advances to unconsolidated affiliates				87,000,000
Retained Earnings
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting policy	21,000,000			$ 144,000,000
Retained Earnings | Accounting Standards Update 2016-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting policy	21,000,000
Unamortized deferred gain	$ 7,000,000