Computation of Basic/Diluted Earnings Per Common Share (Details) - shares shares in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Unvested restricted stock units participating in earnings (in shares)	0	3	0	3
Performance shares not included in dilutive shares (performance measures not yet met)	9	10	9	10
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	0	4	5	4

This element represents nonvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid). Basic and dilutive earnings per share are generally disclosed for such shares using the two-class method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 61A
-URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780137-109256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Participating Security
-URI http://asc.fasb.org/extlink&oid=6519812

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60A
-URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780132-109256

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 59A
-URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780131-109256

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780133-109256

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 68B
-URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5498026-109256

Name:	us-gaap_IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration