Commitments and Contingencies (Employee Benefits Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) plans	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Number of defined contribution 401 (k) plans \| plans	3
Defined contribution plan, contributions \| $	$ 31	$ 26	$ 23

Amount of cost for defined contribution plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration