Organization and Business Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 22, 2010
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable interest entity, ownership percentage		85.00%
Variable interest entity acquisition, percentage of voting interests acquired				15.00%
Variable interest entity acquisition, cost of acquired entity, cash paid	$ 0	$ 9,785	$ 0

The cash outflow associated with the purchase of noncontrolling interest during the period.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 17

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3213-108585

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