Capital Transactions - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended	6 Months Ended
May 06, 2020	Feb. 06, 2020	May 09, 2019	Feb. 12, 2019	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Dividends
Dividends per common share (in dollars per share)		$ 0.41		$ 0.37	$ 0.41	$ 0.37
Cash dividend payment	$ 316		$ 283				$ 316	$ 283

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration