FAIR VALUES OF FINANCIAL INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Unsecured loans receivable, net	$ 35,307	$ 21,862
Liabilities:
Redeemable OP unitholder interests	248,100	159,100
Government-sponsored pooled loan investments
Assets:
Marketable securities	63,322	63,115
Carrying Amount
Assets:
Cash and cash equivalents	120,225	55,348
Secured loans receivable, net	710,451	766,641
Unsecured loans receivable, net	35,307	21,862
Liabilities:
Senior notes payable and other debt, gross	11,584,842	10,872,371
Derivative instruments and other liabilities	1,740	2,743
Redeemable OP unitholder interests	248,129	159,134
Carrying Amount \| Government-sponsored pooled loan investments
Assets:
Marketable securities	63,322	63,115
Carrying Amount \| Marketable securities
Assets:
Marketable securities		77,350	76,046
Fair Value
Assets:
Cash and cash equivalents	120,225	55,348
Secured loans receivable, net	745,394	774,789
Unsecured loans receivable, net	37,185	23,164
Liabilities:
Senior notes payable and other debt, gross	12,181,893	11,197,131
Derivative instruments and other liabilities	1,740	2,743
Redeemable OP unitholder interests	248,129	159,134
Fair Value \| Government-sponsored pooled loan investments
Assets:
Marketable securities	63,322	63,115
Fair Value \| Marketable securities
Assets:
Marketable securities		$ 77,350	$ 76,046

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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Derivative instrument obligations meeting the definition of a liability which the entity is a party to and other liabilities not separately disclosed by the entity as of the balance sheet date.

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Mortgage Loans On Real Estate, Fair Value

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For an unclassified balance sheet, an unsecured amount representing an agreement for an unconditional promise by the maker to pay the Entity (holder) a definite sum of money at a future date, net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

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