Income Taxes Income Taxes - Income Tax Examinations (Details) (USD $)	Mar. 31, 2013 tax_return	Dec. 31, 2007 Internal Revenue Service	Dec. 31, 2010 State
Income Tax Examination [Line Items]
Adjustment as a result of tax return audit		$ 0	$ 0
Number of tax returns under examination	0

The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

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