Merger (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 08, 2018
Merger [Abstract]
Sale of Stock, Price Per Share			$ 15.25
Sale of Stock, Consideration Received on Transaction	$ 5,600
Payments for Merger Related Costs	$ 31	$ 0

The amount of cash paid during the reporting period for charges associated with the mergers.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

Name:	us-gaap_PaymentsForMergerRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration