REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Schedule of Real Estate Properties Acquired (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Purchase Price	$ 219,456	$ 254,497	$ 289,268
Total real estate acquired via foreclosure	6,700	0	0
Mortgage loans on real estate, carrying amount	2,314,109
Net Lease | Jacksonville, NC
Business Acquisition [Line Items]
Purchase Price	$ 7,877
Ownership interest (percent)	100.00%
Net Lease | Iberia, MO
Business Acquisition [Line Items]
Purchase Price	$ 1,328
Ownership interest (percent)	100.00%
Net Lease | Isle, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,078
Ownership interest (percent)	100.00%
Net Lease | Pine Island, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,142
Ownership interest (percent)	100.00%
Net Lease | Kings Mountain, NC
Business Acquisition [Line Items]
Purchase Price	$ 21,241
Ownership interest (percent)	100.00%
Net Lease | Village of Menomonee Falls, WI
Business Acquisition [Line Items]
Purchase Price	$ 17,050
Ownership interest (percent)	100.00%
Net Lease | Rockland, MA
Business Acquisition [Line Items]
Purchase Price	$ 7,316
Ownership interest (percent)	100.00%
Net Lease | Crawfordsville, IA
Business Acquisition [Line Items]
Purchase Price	$ 6,000
Ownership interest (percent)	100.00%
Net Lease | Boardman Township, OH
Business Acquisition [Line Items]
Purchase Price	$ 5,400
Ownership interest (percent)	100.00%
Net Lease | Durant, OK
Business Acquisition [Line Items]
Purchase Price			$ 4,991
Ownership interest (percent)			100.00%
Net Lease | Hilliard, OH
Business Acquisition [Line Items]
Purchase Price	$ 6,384
Ownership interest (percent)	100.00%
Net Lease | Weathersfield Township, OH
Business Acquisition [Line Items]
Purchase Price	$ 5,200
Ownership interest (percent)	100.00%
Net Lease | Rotterdam, NY
Business Acquisition [Line Items]
Purchase Price	$ 12,000
Ownership interest (percent)	100.00%
Net Lease | Wheaton, MO
Business Acquisition [Line Items]
Purchase Price	$ 970
Ownership interest (percent)	100.00%
Net Lease | Paynesville, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,254
Ownership interest (percent)	100.00%
Net Lease | Loveland, CO
Business Acquisition [Line Items]
Purchase Price	$ 5,600
Ownership interest (percent)	100.00%
Net Lease | Battle Lake, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,098
Ownership interest (percent)	100.00%
Net Lease | Yorktown, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,207
Ownership interest (percent)	100.00%
Net Lease | St. Francis, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,117
Ownership interest (percent)	100.00%
Net Lease | Red Oak, IA
Business Acquisition [Line Items]
Purchase Price	$ 1,185
Ownership interest (percent)	100.00%
Net Lease | Zapata, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,150
Ownership interest (percent)	100.00%
Net Lease | Aurora, MN
Business Acquisition [Line Items]
Purchase Price	$ 952
Ownership interest (percent)	100.00%
Net Lease | Canyon Lake, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,377
Ownership interest (percent)	100.00%
Net Lease | Wheeler, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,075
Ownership interest (percent)	100.00%
Net Lease | Bridgeport, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,186
Ownership interest (percent)	100.00%
Net Lease | Peoria, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,226
Ownership interest (percent)	100.00%
Net Lease | Pleasanton, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,316
Ownership interest (percent)	100.00%
Net Lease | Warren, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,055
Ownership interest (percent)	100.00%
Net Lease | Tremont, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,150
Ownership interest (percent)	100.00%
Net Lease | Ponce, Puerto Rico
Business Acquisition [Line Items]
Purchase Price	$ 8,900
Ownership interest (percent)	100.00%
Net Lease | Effingham County, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,195
Ownership interest (percent)	100.00%
Net Lease | Lebanon, MI
Business Acquisition [Line Items]
Purchase Price	$ 1,200
Ownership interest (percent)	100.00%
Net Lease | Minot, ND
Business Acquisition [Line Items]
Purchase Price	$ 6,644
Ownership interest (percent)	100.00%
Net Lease | Floresville, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,251
Ownership interest (percent)	100.00%
Net Lease | Kerrville, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,174
Ownership interest (percent)	97.00%
Net Lease | De Soto, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,066
Ownership interest (percent)	97.00%
Net Lease | Biscoe, NC
Business Acquisition [Line Items]
Purchase Price	$ 1,216
Ownership interest (percent)	100.00%
Net Lease | Moultrie, GA
Business Acquisition [Line Items]
Purchase Price	$ 1,305
Ownership interest (percent)	100.00%
Net Lease | Rose Hill, NC
Business Acquisition [Line Items]
Purchase Price	$ 1,420
Ownership interest (percent)	100.00%
Net Lease | Rockingham, NC
Business Acquisition [Line Items]
Purchase Price	$ 1,158
Ownership interest (percent)	100.00%
Net Lease | Wilmington, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,309
Ownership interest (percent)	100.00%
Net Lease | Danville, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,074
Ownership interest (percent)	100.00%
Net Lease | Bloomington, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,193
Ownership interest (percent)	100.00%
Net Lease | Lincoln County, MO
Business Acquisition [Line Items]
Purchase Price	$ 1,072
Ownership interest (percent)	100.00%
Net Lease | Montrose, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,167
Ownership interest (percent)	100.00%
Net Lease | Jenks, OK
Business Acquisition [Line Items]
Purchase Price	$ 12,160
Ownership interest (percent)	100.00%
Net Lease | Grove, OK
Business Acquisition [Line Items]
Purchase Price	$ 5,030
Ownership interest (percent)	100.00%
Net Lease | Farmington, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,303
Ownership interest (percent)	100.00%
Net Lease | Bixby, OK
Business Acquisition [Line Items]
Purchase Price	$ 10,978
Ownership interest (percent)	100.00%
Net Lease | Rice, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,200
Ownership interest (percent)	100.00%
Net Lease | Gordonville, MO
Business Acquisition [Line Items]
Purchase Price	$ 1,125
Ownership interest (percent)	100.00%
Net Lease | Malone, NY
Business Acquisition [Line Items]
Purchase Price	$ 1,466
Ownership interest (percent)	100.00%
Net Lease | Mercedes, TX
Business Acquisition [Line Items]
Purchase Price	$ 1,204
Ownership interest (percent)	100.00%
Net Lease | Albion, PA
Business Acquisition [Line Items]
Purchase Price	$ 1,525
Ownership interest (percent)	100.00%
Net Lease | Radford, VA
Business Acquisition [Line Items]
Purchase Price	$ 1,564
Ownership interest (percent)	100.00%
Net Lease | Rural Retreat, VA
Business Acquisition [Line Items]
Purchase Price	$ 1,399
Ownership interest (percent)	100.00%
Net Lease | Mount Vernon, AL
Business Acquisition [Line Items]
Purchase Price	$ 1,224
Ownership interest (percent)	100.00%
Net Lease | O'Fallon, IL
Business Acquisition [Line Items]
Purchase Price		$ 8,000
Ownership interest (percent)		100.00%
Net Lease | El Centro, CA
Business Acquisition [Line Items]
Purchase Price		$ 4,277
Ownership interest (percent)		100.00%
Net Lease | Conyers, GA
Business Acquisition [Line Items]
Purchase Price		$ 32,530
Ownership interest (percent)		100.00%
Net Lease | Bennett, CO
Business Acquisition [Line Items]
Purchase Price		$ 3,522
Ownership interest (percent)		100.00%
Net Lease | Memphis, TN
Business Acquisition [Line Items]
Purchase Price		$ 5,310
Ownership interest (percent)		100.00%
Net Lease | Ankeny, IA
Business Acquisition [Line Items]
Purchase Price		$ 16,510
Ownership interest (percent)		100.00%
Net Lease | Springfield, MO
Business Acquisition [Line Items]
Purchase Price		$ 11,675
Ownership interest (percent)		100.00%
Net Lease | Sheldon, IA
Business Acquisition [Line Items]
Purchase Price		$ 4,300
Ownership interest (percent)		100.00%
Net Lease | Cedar Rapids, IA
Business Acquisition [Line Items]
Purchase Price		$ 11,000
Ownership interest (percent)		100.00%
Net Lease | Fairfield, IA
Business Acquisition [Line Items]
Purchase Price		$ 10,695
Ownership interest (percent)		100.00%
Net Lease | Muscatine, IA
Business Acquisition [Line Items]
Purchase Price		$ 7,150
Ownership interest (percent)		100.00%
Net Lease | Owatonna, MN
Business Acquisition [Line Items]
Purchase Price		$ 9,970
Ownership interest (percent)		100.00%
Net Lease | Bellport, NY
Business Acquisition [Line Items]
Purchase Price		$ 18,100
Ownership interest (percent)		100.00%
Net Lease | Woodland Park, CO
Business Acquisition [Line Items]
Purchase Price		$ 3,969
Ownership interest (percent)		100.00%
Net Lease | Evansville, IN
Business Acquisition [Line Items]
Purchase Price		$ 9,000
Ownership interest (percent)		100.00%
Net Lease | Plattsmouth, NE
Business Acquisition [Line Items]
Purchase Price		$ 7,979
Ownership interest (percent)		100.00%
Net Lease | Worthington, MN
Business Acquisition [Line Items]
Purchase Price		$ 8,320
Ownership interest (percent)		100.00%
Other
Business Acquisition [Line Items]
Ownership interest (percent)	100.00%
Other | Grand Rapids, MI
Business Acquisition [Line Items]
Purchase Price	$ 9,300
Ownership interest (percent)	97.00%
Other | Grand Rapids, MI
Business Acquisition [Line Items]
Purchase Price	$ 6,300
Ownership interest (percent)	97.00%
Other | Wayne, NJ
Business Acquisition [Line Items]
Purchase Price	$ 9,700
Ownership interest (percent)	100.00%
Other | Richmond, VA
Business Acquisition [Line Items]
Purchase Price		$ 19,850	$ 134,999
Ownership interest (percent)		77.50%	77.50%
Other | St. Paul, MN
Business Acquisition [Line Items]
Purchase Price		$ 62,340
Ownership interest (percent)		97.00%
Other | Carmel, NY
Business Acquisition [Line Items]
Total real estate acquired via foreclosure	$ 6,700
Gain on sale of mortgage loans	800
Mortgage loans on real estate, carrying amount	5,900
Other | Southfield, MI
Business Acquisition [Line Items]
Purchase Price			$ 18,000
Ownership interest (percent)			90.00%
Office building | Minneapolis, MN
Business Acquisition [Line Items]
Purchase Price			$ 51,278
Ownership interest (percent)			90.00%
Condominium | Miami, FL
Business Acquisition [Line Items]
Purchase Price			$ 80,000
Ownership interest (percent)			100.00%
Real Estate
Business Acquisition [Line Items]
Purchase Price	$ 212,756