SENIOR NOTES PAYABLE AND OTHER DEBT (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	$ 743,060,000
2016	900,750,000
2017	894,015,000
2018	1,576,195,000
2019	2,266,621,000
Thereafter	5,204,201,000
Total	11,584,842,000	10,872,371,000
Unrestricted cash and cash equivalents	120,225,000	55,348,000	59,791,000	94,816,000
Amount outstanding, net of cash and cash equivalents	177,800,000
Principal Amount Due at Maturity
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	710,661,000
2016	861,817,000
2017	865,425,000
2018	1,101,879,000
2019	2,251,927,000
Thereafter	5,055,379,000
Total	10,847,088,000
Unsecured Revolving Credit Facility
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	0
2016	0
2017	0
2018	451,924,000
2019	0
Thereafter	0
Total	451,924,000	919,099,000
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	32,399,000
2016	38,933,000
2017	28,590,000
2018	22,392,000
2019	14,694,000
Thereafter	148,822,000
Total	285,830,000
Senior Notes | 6.90% Senior Notes due 2037
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Thereafter	52,400,000
Interest rate (as a percent)		6.90%
Senior Notes | 6.59% senior notes due 2038
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Thereafter		$ 23,000,000
Interest rate (as a percent)		6.59%