Transactions with Related Parties (Details) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Related Party Transaction [Line Items]
rate for administration fees	0.45%
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Administrative Fees, Amount Paid	$ 33,000
Majority-Owned Subsidiary, Unconsolidated [Member]
Related Party Transaction [Line Items]
Administrative Fees, Amount Paid	$ 342,000	$ 194,000

Amount paid to managing member or general partner, affiliate of managing member or general partner, or affiliate of limited liability company (LLC) or limited partnership (LP) for administrative services provided to the LLC or LP, for example, but not limited to, salaries, rent, or other overhead costs.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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