FINANCIAL INSTRUMENTS (Schedule of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
4.375% notes due 2023
Liabilities:
Notes issued, interest rate	4.375%	4.375%
4.95% notes due 2024
Liabilities:
Notes issued, interest rate	4.95%	4.95%
4.50% notes due 2025
Liabilities:
Notes issued, interest rate	4.50%	4.50%
5.25% notes due 2026
Liabilities:
Notes issued, interest rate	5.25%	5.25%
4.50% notes due 2027
Liabilities:
Notes issued, interest rate	4.50%	4.50%
4.75% notes due 2028
Liabilities:
Notes issued, interest rate	4.75%	4.75%
3.625% notes due 2029
Liabilities:
Notes issued, interest rate	3.625%
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets:
Investments in direct financing leases - net	$ 11,488	$ 132,262
Mortgage notes receivable - net	773,563	710,858
Other investments - net	419,228	504,626
Total	1,204,279	1,347,746
Liabilities:
Revolving line of credit	125,000	313,000
Secured borrowing	2,275
U.S. term loan	348,878	423,065
Sterling term loan	132,059	127,394
Omega OP term loan	74,763	99,553
2015 term loan	249,038	248,713
Subordinated debt - net	13,714	20,270
Total	5,136,140	4,540,622
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 4.375% notes due 2023
Liabilities:
Notes Payable	695,812	694,643
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 4.95% notes due 2024
Liabilities:
Notes Payable	395,702	394,691
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 4.50% notes due 2025
Liabilities:
Notes Payable	396,163	395,402
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 5.25% notes due 2026
Liabilities:
Notes Payable	595,732	595,027
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 4.50% notes due 2027
Liabilities:
Notes Payable	689,445	687,981
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 4.75% notes due 2028
Liabilities:
Notes Payable	541,891	540,883
Carrying (Reported) Amount, Fair Value Disclosure [Member] | 3.625% notes due 2029
Liabilities:
Notes Payable	488,263
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Hud Mortgage Assumed [Member]
Liabilities:
HUD debt - net	387,405
Estimate Of Fair Value, Fair Value Disclosure [Member]
Assets:
Investments in direct financing leases - net	11,488	132,262
Mortgage notes receivable - net	819,083	735,892
Other investments - net	412,934	503,907
Total	1,243,505	1,372,061
Liabilities:
Revolving line of credit	125,000	313,000
Secured borrowing	2,275
U.S. term loan	350,000	425,000
Sterling term loan	132,480	127,990
Omega OP term loan	75,000	100,000
2015 term loan	250,000	250,000
Subordinated debt - net	15,253	22,589
Total	5,490,735	4,551,912
Estimate Of Fair Value, Fair Value Disclosure [Member] | 4.375% notes due 2023
Liabilities:
Notes Payable	749,693	700,062
Estimate Of Fair Value, Fair Value Disclosure [Member] | 4.95% notes due 2024
Liabilities:
Notes Payable	442,327	406,386
Estimate Of Fair Value, Fair Value Disclosure [Member] | 4.50% notes due 2025
Liabilities:
Notes Payable	430,529	392,122
Estimate Of Fair Value, Fair Value Disclosure [Member] | 5.25% notes due 2026
Liabilities:
Notes Payable	675,078	605,700
Estimate Of Fair Value, Fair Value Disclosure [Member] | 4.50% notes due 2027
Liabilities:
Notes Payable	759,475	671,555
Estimate Of Fair Value, Fair Value Disclosure [Member] | 4.75% notes due 2028
Liabilities:
Notes Payable	602,967	$ 537,508
Estimate Of Fair Value, Fair Value Disclosure [Member] | 3.625% notes due 2029
Liabilities:
Notes Payable	500,792
Estimate Of Fair Value, Fair Value Disclosure [Member] | Hud Mortgage Assumed [Member]
Liabilities:
HUD debt - net	$ 379,866