SENIOR NOTES PAYABLE AND OTHER DEBT - Indebtedness of Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	$ 7,467
2017	657,946
2018	1,355,369
2019	1,717,257
2020	1,428,533
Thereafter	6,151,265
Total maturities	11,317,837	$ 11,271,020
Unrestricted cash and cash equivalents	89,279	53,023	$ 65,231	$ 55,348
Amount outstanding, net of cash and cash equivalents	143,100
Principal Amount Due at Maturity
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	0
2017	631,902
2018	1,101,879
2019	1,702,650
2020	1,416,913
Thereafter	6,023,925
Total maturities	10,877,269
Unsecured Revolving Credit Facility
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	0
2017	0
2018	232,405
2019	0
2020	0
Thereafter	0
Total maturities	232,405	180,683
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2016	7,467
2017	26,044
2018	21,085
2019	14,607
2020	11,620
Thereafter	127,340
Total maturities	208,163
Mortgage Loans Held-for-Sale
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	66,000	$ 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%