Accounting and Reporting Developments - Additional Information (Details) - USD ($) $ in Millions	Jan. 01, 2019	Jan. 01, 2018
Accounting Policies [Abstract]
Right of use asset and lease liabilities	$ 509
Impact of cumulative effect of change in accounting principles	$ 10	$ 4

Amount of lessee's right to use underlying asset under operating lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

Name:	us-gaap_OperatingLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant