SENIOR NOTES PAYABLE AND OTHER DEBT - Indebtedness of Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2019	$ 434,498
2020	318,762
2021	1,146,560
2022	1,271,824
2023	1,612,450
Thereafter	7,356,326
Long-term debt and short-term borrowings, gross	12,140,420	$ 10,829,702
Line of Credit Facility and Commercial Paper Program amount outstanding	1,100,000
Unrestricted cash and cash equivalents	148,063	$ 72,277
Unsecured Revolving Credit Facility and Commercial Paper
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2019	305,000
2020	0
2021	983,788
2022	0
2023	0
Thereafter	0
Long-term debt and short-term borrowings, gross	1,288,788
Principal Amount Due at Maturity
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2019	119,214
2020	280,835
2021	126,121
2022	1,240,945
2023	1,595,197
Thereafter	7,268,882
Long-term debt and short-term borrowings, gross	10,631,194
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2019	10,284
2020	37,927
2021	36,651
2022	30,879
2023	17,253
Thereafter	87,444
Long-term debt and short-term borrowings, gross	$ 220,438