Other Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Straight-line rent receivables, net	$ 120,325	$ 96,883
Marketable debt securities	5,400	43,331
Unsecured loans receivable, net	62,118	63,598
Goodwill and other intangibles, net	515,429	462,655
Assets held for sale	111,556	119,290
Other	106,857	105,475
Total other assets	$ 921,685	$ 891,232

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property, by the lessor or lessee, respectively. Such receivable is reduced by allowances attributable to, for instance, credit risk associated with a lessee.

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