USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Components of Balance Sheet and Income Statement Location (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance sheet-related [Abstract]
Swap agreements in a gain position (an asset) related to borrowings			$ 24,709
Swap agreements in a loss position (a liability) related to borrowings		$ (23,772)	(24,417)
Interest rate swap agreements at fair value, net assets (liability)		(24,256)	(11,697)
Income statement-related [Abstract]
Amount of gain (loss) reclassified from Accumulated other comprehensive income		(4,808)	19,955	$ 28,550
Other comprehensive income (loss)-related [Abstract]
Amount of gain (loss) recognized in Other comprehensive income		21,531	(1,370)	(21,675)
Interest Expense [Member]
Income statement-related [Abstract]
Decrease (increase) in interest expense and increase(decrease) in Net income as a result of the use of Derivatives		4,448	(21,191)	(29,474)
Secured Borrowings [Member] | Interest Expense [Member]
Income statement-related [Abstract]
Amount of gain (loss) reclassified from Accumulated other comprehensive income		7,686	(17,180)	(28,266)
Amount of (loss) recognized in income		(360)	(1,236)	(924)
Decrease (increase) in interest expense and increase(decrease) in Net income as a result of the use of Derivatives	[1]	7,326	(18,416)	(29,190)
Unsecured Borrowings [Member] | Interest Expense [Member]
Income statement-related [Abstract]
Amount of gain (loss) reclassified from Accumulated other comprehensive income	[2]	(2,878)	(2,775)	$ (284)
Receivable and Other Assets [Member] | Interest Rate Swap Agreements [Member] | Secured Borrowings [Member]
Balance sheet-related [Abstract]
Swap agreements in a gain position (an asset) related to borrowings	[3]		24,709
Accounts Payable and Accrued Liabilities [Member]
Balance sheet-related [Abstract]
Related net interest payable	[4]	(484)	(11,989)
Interest Rate Swap Agreements at Fair Value [Member] | Secured Borrowings [Member]
Balance sheet-related [Abstract]
Swap agreements in a loss position (a liability) related to borrowings	[3]		(222)
Interest Rate Swap Agreements at Fair Value [Member] | Unsecured Borrowings [Member]
Balance sheet-related [Abstract]
Swap agreements in a loss position (a liability) related to borrowings	[3]	$ (23,772)	$ (24,195)

[1] Included in “Interest expense: Secured borrowings” on the face of the Statements of Income.

[2] Included in “Interest expense: Unsecured borrowings” on the face of the Statements of Income

[3] The fair value of Derivatives with unrealized gains are aggregated and recorded as an asset on the face of the Balance Sheets separately from the fair value of Derivatives with unrealized losses that are recorded as a liability. The amount of unrealized gains, net of unrealized losses, scheduled to be recognized in the Statements of Income over the next twelve months primarily in the form of current market rates in excess of fixed-rate swap payments totaled $22.4 million at December 31, 2017.

[4] Included in “Accounts payable and accrued expenses” on the face of the Balance Sheets.