Represents the total number of common shares of beneficial interest of equity method investee owned by an investor.

Name:	cwh_EquityMethodInvestmentNumberOfSharesOwned
Namespace Prefix:	cwh
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of ownership of common stock or equity participation in the investee formerly held by the entity.

+ Details

Name:	cwh_EquityMethodInvestmentOwnershipPercentageFormerlyHeld
Namespace Prefix:	cwh
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The entity owns less than this percentage of an equity method investment.

+ Details

Name:	cwh_EquityMethodInvestmentOwnershipPercentageHeld
Namespace Prefix:	cwh
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the amount of premiums for property insurance pursuant to an insurance program arranged by the equity method investee.

+ Details

Name:	cwh_EquityMethodInvestmentPropertyInsurancePremiumAmount
Namespace Prefix:	cwh
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of premiums for property insurance pursuant to an insurance program arranged by the equity method investee incurred during the period.

+ Details

Name:	cwh_EquityMethodInvestmentPropertyInsurancePremiumIncurred
Namespace Prefix:	cwh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the quoted market price per common share for those investments which are accounted for under the equity method.

+ Details

Name:	cwh_EquityMethodInvestmentQuotedMarketPricePerShare
Namespace Prefix:	cwh
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of entities to which related party of the entity provides management services.

+ Details

Name:	cwh_NumberOfEntitiesToWhichRelatedPartyProvidesManagementServices
Namespace Prefix:	cwh
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of other shareholders of related party of the entity.

+ Details

Name:	cwh_NumberOfOtherShareholdersOfRelatedParty
Namespace Prefix:	cwh
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the number of properties sold or agreed to be sold by the entity.

+ Details

Name:	cwh_NumberOfPropertiesSold
Namespace Prefix:	cwh
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the period for which the term of property insurance program is extended.

+ Details

Name:	cwh_PeriodForWhichPropertyInsuranceProgramExtended
Namespace Prefix:	cwh
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the aggregate sales price excluding closing costs, of real estate properties sold or agreed to be sold by the entity.

+ Details

Name:	cwh_RealEstateAggregateSalesPrice
Namespace Prefix:	cwh
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenses recognized during the period resulting from business management transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ Details

Name:	cwh_RelatedPartyTransactionExpensesFromBusinessManagementAgreementTransactionsWithRelatedParty
Namespace Prefix:	cwh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Expenses recognized during the period resulting from property management transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ Details

Name:	cwh_RelatedPartyTransactionExpensesFromPropertyManagementAgreementTransactionsWithRelatedParty
Namespace Prefix:	cwh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 12

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-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 AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the aggregate value of each identified investment accounted for under the equity method of accounting based on the quoted market price for those investments in common stock for which a quoted market price is available.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-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 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentQuotedMarketValue
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6382870&loc=d3e33749-111570

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6382870&loc=d3e33749-111570

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-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 Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 9

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

+ Details

Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of states the entity operates in as of the balance sheet date.

+ Details

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of square footage related to a real estate property.

+ Details

Name:	us-gaap_SquareFootageOfRealEstateProperty
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

Related Person Transactions (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended			12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	1 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 sqft property quarter officetower	Sep. 30, 2010 sqft	Dec. 31, 2010	Dec. 31, 2010 GOV property	Sep. 30, 2011 GOV	Sep. 30, 2011 AIC entity	Sep. 30, 2010 AIC	Sep. 30, 2011 AIC Y entity	Sep. 30, 2010 AIC	Dec. 31, 2010 AIC	Sep. 30, 2011 SNH property sqft state	Jun. 30, 1999 SNH	Sep. 30, 2011 SNH Agreement to sell	Nov. 30, 2010 SNH Agreement to sell property sqft	Sep. 30, 2011 RMR	Sep. 30, 2010 RMR	Sep. 30, 2011 RMR	Sep. 30, 2010 RMR	Sep. 30, 2011 Agreement to sell sqft property
Related person transactions
Business management agreement expense																	$ 9,862	$ 8,881	$ 27,844	$ 26,053
Property management agreement expense																	7,767	6,592	21,487	19,878
Equity method investments, ownership percentage formerly held							100.00%
Equity investments, common shares owned (in shares)							9,950,000
Equity method investments, ownership percentage							21.10%	14.29%		14.29%				100.00%
Equity investments	178,652		178,652		171,464	166,388	173,407	5,245		5,245		5,076
Equity investments, market value based on quoted market prices							214,025
Equity investments, quoted market price of common share (in dollars per share)						$ 26.79	$ 21.51
Number of properties sold or agreed to be sold						15							13			27					16
Property square feet			69,399,000	59,430,000									1,310,000			2,803,000					570,000
Aggregate sale price of properties sold or agreed to be sold, excluding closing costs															167,000	470,000					6,500
Number of states in which properties are located													8
Number of other shareholders of related party								6		6
Number of companies to which RMR provides management services								5		5
Ownership percentage in equity method investment								20.00%		20.00%
Amount invested in equity investee								5,209		5,209
Income (loss) from equity method investments	2,768	1,999	8,390	6,643				28	35	111	(17)
Period for which property insurance program was extended (in years)										1
Premium for property insurance										5,540		5,328
Amount expensed in relation to insurance premiums								$ 1,385	$ 1,332	$ 4,067	$ 1,776