Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

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

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
Subsequent Events (Details) - USD ($) $ in Millions	Jul. 31, 2016	Jan. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jul. 01, 2016
Subsequent Event [Line Items]
Redeemed notes		$ 125
Gain (loss) on extinguishment of debt			$ 0	$ (117)	$ 4	$ (141)
Senior Notes [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Redeemed notes	$ 181
Debt Instrument, Interest Rate, Stated Percentage							8.00%
Gain (loss) on extinguishment of debt	$ 16