Fair Value of Certain Financial Assets and Liabilities and Other Financial Instruments (Detail) (USD $) In Millions	Dec. 31, 2010	Dec. 31, 2009
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets
Mortgage notes	$ 55
Other notes receivable		11
Financial liabilities
Senior notes	3,093	3,411
Exchangeable Senior Debentures	1,156	1,123
Credit facility	58
Mortgage debt and other, net of capital leases	1,110	1,302
Portion at Fair Value, Fair Value Disclosure
Financial assets
Mortgage notes	77
Other notes receivable		11
Financial liabilities
Senior notes	3,200	3,473
Exchangeable Senior Debentures	1,471	1,246
Credit facility	58
Mortgage debt and other, net of capital leases	$ 1,107	$ 1,269

Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Exchangeable Senior Debentures

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Financial Assets [Abstract]

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Financial Liabilities [Abstract]

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Fair Value Option Disclosures Not Related to Election Items Existing At Effective Date Line Of Credit

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Mortgage Debt and Other, Net of Capital Leases

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Mortgage Notes Receivable

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Other Notes Receivable

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Fair Value, Option, Disclosures Not Related to Election, Items Existing at Effective Date, Senior Debt Obligations

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