Noncontrolling Interests (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of redeemable noncontrolling interests
Beginning balance, Redeemable Noncontrolling Interests	$ 5,799	$ 4,369	$ 4,008
Noncontrolling interest, Income Statement Impact	840	757	632
Redemption value change, Income Statement Impact	716
Redemption value change, Redeemable Noncontrolling Interests	1,555	757	632
Formation of noncontrolling interests, Redeemable Noncontrolling Interests	510	1,390	370
Distribution to noncontrolling interests, Redeemable Noncontrolling Interests	(901)	(717)	(641)
Ending balance, Redeemable Noncontrolling Interests	$ 6,964	$ 5,799	$ 4,369

As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Subparagraph (12)(c)

-Section S99

-Paragraph 3A

-URI http://asc.fasb.org/extlink&oid=6802392&loc=SL6540498-122764

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Subparagraph 14

-Paragraph 3A

-Section S99

-URI http://asc.fasb.org/extlink&oid=6802392&loc=SL6540498-122764

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number D-98

-Paragraph 43

-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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Subparagraph 15

-Paragraph 3A

-Section S99

-URI http://asc.fasb.org/extlink&oid=6802392&loc=SL6540498-122764

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number D-98

-Paragraph 43

-Subparagraph c

-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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 27

-Appendix A

-Subparagraph c

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Subparagraph (16)(c)

-Paragraph 3A

-Section S99

-URI http://asc.fasb.org/extlink&oid=6802392&loc=SL6540498-122764

+ Details