Contingencies Contingencies - Other (Details) (Third Party Bankruptcy Assignment [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2013
Third Party Bankruptcy Assignment [Member]
Loss Contingencies [Line Items]
Pretax loss	$ 141
Decommissioning obligations included in accrued expenses	56
Decommissioning obligations included in other long-term liabilities	$ 85

The portion of the carrying amount as of the balance sheet date of the combined total of loss contingency liabilities which is expected to be resolved after one year or beyond the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_LossContingencyAccrualCarryingValueNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant