Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Diluted Earnings Per Share
-URI http://asc.fasb.org/extlink&oid=6510752

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Stock Agreement
-URI http://asc.fasb.org/extlink&oid=6508534

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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

Basis of Presentation - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Dec. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Employee Stock Option [Member]
Subsidiary or Equity Method Investee [Line Items]
Shares excluded from diluted EPS calculation		4.7	3.7	5.1	3.6
Accounting Standards Update 2015-03 [Member]
Subsidiary or Equity Method Investee [Line Items]
Decrease in other assets and long term debt	$ 23
CNA Financial [Member]
Subsidiary or Equity Method Investee [Line Items]
Subsidiary ownership percentage				90.00%
Diamond Offshore Drilling, Inc. [Member]
Subsidiary or Equity Method Investee [Line Items]
Subsidiary ownership percentage				53.00%
Boardwalk Pipeline Partners, LP [Member]
Subsidiary or Equity Method Investee [Line Items]
Subsidiary ownership percentage				51.00%