Income Taxes - Out of Period Adjustments (Details) (Income tax benefit related to 2012 and 2011, USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2013
Income tax benefit related to 2012 and 2011
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Out of period adjustments	$ (3)

Amount of each individual error being corrected in the correcting adjustment.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 250

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 1.N.Q3)

-URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 1

-Section N

Name:	us-gaap_QuantifyingMisstatementInCurrentYearFinancialStatementsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration