Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2011
Accounting Policies [Abstract]
Consolidation [Policy Text Block]	The consolidated financial statements reflect all of our accounts, including those of our majority-owned and/or controlled subsidiaries. The portion of equity in a subsidiary that is not attributable, directly or indirectly, to us is presented as noncontrolling interests. All significant intercompany accounts and transactions have been eliminated
Finance, Loans and Leases Receivable, Policy [Policy Text Block]	Assets representing rights to receive money on demand or at fixed or determinable dates are referred to as finance receivables. Our finance receivable portfolios consist of direct financing leases and deferred acquisition fees. Operating leases are not included in finance receivables as such amounts are not recognized as an asset in the consolidated balance sheets
Equity Method Investments, Policy [Policy Text Block]	We own interests in the REITs and account for these interests under the equity method because, as their advisor and through our ownership in their common shares, we do not exert control but have the ability to exercise significant influence. Shares of the REITs are publicly registered and the REITs file periodic reports with the SEC, but the shares are not listed on any exchange and are not actively traded. We earn asset management and performance revenue from the REITs and have elected, in certain cases, to receive a portion of this revenue in the form of restricted common stock of the REITs rather than cash. We own interests in single-tenant net leased properties leased to corporations through noncontrolling interests in (i) partnerships and limited liability companies that we do not control but over which we exercise significant influence, and (ii) as tenants-in-common subject to common control. Generally, the underlying investments are jointly-owned with affiliates. We account for these investments under the equity method of accounting (i.e., at cost, increased or decreased by our share of earnings or losses, less distributions, plus contributions and other adjustments required by equity method accounting, such as basis differences from other-than-temporary impairments).
Fair Value of Financial Instruments, Policy [Policy Text Block]	Under current authoritative accounting guidance for fair value measurements, the fair value of an asset is defined as the exit price, which is the amount that would either be received when an asset is sold or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The guidance establishes a three-tier fair value hierarchy based on the inputs used in measuring fair value. These tiers are: Level 1, for which quoted market prices for identical instruments are available in active markets, such as money market funds, equity securities and U.S. Treasury securities; Level 2, for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument, such as certain derivative instruments including interest rate caps and swaps; and Level 3, for which little or no market data exists, therefore requiring us to develop our own assumptions, such as certain securities. Items Measured at Fair Value on a Recurring Basis The following methods and assumptions were used to estimate the fair value of each class of financial instrument: Money Market Funds — Our money market funds consisted of government securities and U.S. Treasury bills. These funds were classified as Level 1 as we used quoted prices from active markets to determine their fair values Derivative Assets and Liabilities — Our derivative assets and liabilities primarily comprised of interest rate swaps or caps. These derivative instruments were measured at fair value using readily observable market inputs, such as quotations on interest rates. Our derivative instruments were classified as Level 2 as these instruments are custom, over-the-counter contracts with various bank counterparties that are not traded in an active market. Other Securities — Our other securities primarily comprised of our investment in an India growth fund and our interest in a commercial mortgage loan securitization. These funds are not traded in an active market. We estimated the fair value of these securities using internal valuation models that incorporate market inputs and our own assumptions about future cash flows. We classified these assets as Level 3. Redeemable Noncontrolling Interest — We account for the noncontrolling interest in WPCI as redeemable noncontrolling interest. We determined the valuation of redeemable noncontrolling interest using widely accepted valuation techniques, including discounted cash flow on the expected cash flows of the investment as well as the income capitalization approach, which considers prevailing market capitalization rates. We classified this liability as Level 3
Shares Subject to Mandatory Redemption, Changes in Redemption Value, Policy [Policy Text Block]	We account for the noncontrolling interest in WPCI held by one of our officers as a redeemable noncontrolling interest, as we have an obligation to repurchase the interest from that officer, subject to certain conditions. The officer's interest is reflected at estimated redemption value for all periods presented.
Discontinued Operations, Policy [Policy Text Block]	From time to time, tenants may vacate space due to lease buy-outs, elections not to renew their leases, insolvency or lease rejection in the bankruptcy process. In these cases, we assess whether we can obtain the highest value from the property by re-leasing or selling it. In addition, in certain cases, we may try to sell a property that is occupied. When it is appropriate to do so under current accounting guidance for the disposal of long-lived assets, we classify the property as an asset held for sale on our consolidated balance sheet and the current and prior period results of operations of the property are reclassified as discontinued operations.

Describes an entity's accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. An entity also may describe its accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

+ References+ Details

Describes an entity's application of the equity method of accounting to investments in common stock or other interests including unconsolidated subsidiaries, corporate joint ventures, noncontrolling interests in real estate ventures, limited partnerships, and limited liability companies. The description should include information such as: (1) initially recording an investment in the stock of an investee at cost; (2) adjusting the carrying amount of the investment to recognize the investor's share of the earnings or losses of the investee after the date of acquisition; and (3) adjustments to reflect the investor's share of changes in the investee's capital (dividends). This disclosure may also include a detailed description of the policy for determining the amount of equity method losses recognized after an investment has been reduced to zero as a result of previous losses, reasons for not using the equity method when the investor company owns 20 percent or more of the voting stock of the investee's company (including identification of the significant investee), reasons for using the equity method when the ownership percentage is less than 20 percent, and discussion of recognition of equity method losses when an investor's total investment in an investee includes, in addition to an investment in common stock, other investments such as preferred stock and loans to the investee. An entity also may describe how such investments are assessed for impairment.

+ References+ Details

- Definition

Describes an entity's accounting policy for finance, loan and lease receivables, including those held for investment and those held for sale. This disclosure may include (1) the basis at which such receivables are carried in the entity's statements of financial position (2) how the level of the allowance for loan and lease losses is determined (3) when impairments, charge-offs or recoveries are recognized for such receivables (4) the treatment of origination fees and costs, including the amortization method for net deferred fees or costs (5) the treatment of any premiums or discounts or unearned income (6) the entity's income recognition (revenues, expenses and gains and losses arising from committing to issue, issuing, granting, collecting, terminating, modifying and holding loans) policies for such receivables, including those that are impaired, past due or placed on nonaccrual status and (7) the treatment of foreclosures or repossessions.

+ References+ Details