SENIOR NOTES PAYABLE AND OTHER DEBT - Indebtedness of Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	$ 119,744
2017	707,414
2018	1,335,212
2019	1,723,427
2020	1,428,395
Thereafter	5,654,079
Total maturities	10,968,271	$ 11,271,020
Unrestricted cash and cash equivalents	57,322	53,023	$ 60,532	$ 55,348
Amount outstanding, net of cash and cash equivalents	155,100
Principal Amount Due at Maturity
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	105,496
2017	681,502
2018	1,101,879
2019	1,708,956
2020	1,416,913
Thereafter	5,526,211
Total maturities	10,540,957
Unsecured Revolving Credit Facility
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	0
2017	0
2018	212,382
2019	0
2020	0
Thereafter	0
Total maturities	212,382	180,683
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	14,248
2017	25,912
2018	20,951
2019	14,471
2020	11,482
Thereafter	127,868
Total maturities	214,932
Mortgage Loans Held-for-Sale
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	77,000	$ 22,900
Senior Notes | 6.90% Senior Notes due 2037, subject to repurchase at option of holders
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	$ 52,400
Interest rate	6.90%
Senior Notes | 6.59% Senior Notes due 2038, subject to repurchase at option of holders
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	$ 23,000
Interest rate	6.59%