Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges on Consolidated Assets (Detail) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Investments Debt And Equity Securities [Abstract]
Assets marketed for sale	$ 6,900,000	$ 1,500,000
Total continuing operations	6,926,000	1,541,000
Sold assets or assets held for sale	800,000	15,800,000
Total discontinued operations	753,000	15,830,000
Joint venture investments	0	560,000
Total impairment charges	$ 7,700,000	$ 17,900,000

The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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