CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total Stockholders' Equity [Member] Scenario, Previously Reported [Member]	Total Stockholders' Equity [Member] Restatement Adjustment [Member]	Total Stockholders' Equity [Member]	Common Stock Scenario, Previously Reported [Member]	Common Stock Restatement Adjustment [Member]	Common Stock	Additional Paid-in Capital Scenario, Previously Reported [Member]	Additional Paid-in Capital Restatement Adjustment [Member]	Additional Paid-in Capital	Cumulative Net Earnings Scenario, Previously Reported [Member]	Cumulative Net Earnings Restatement Adjustment [Member]	Cumulative Net Earnings	Cumulative Dividends Scenario, Previously Reported [Member]	Cumulative Dividends Restatement Adjustment [Member]	Cumulative Dividends	Accumulated Other Comprehensive Loss Scenario, Previously Reported [Member]	Accumulated Other Comprehensive Loss Restatement Adjustment [Member]	Accumulated Other Comprehensive Loss	Noncontrolling Interest Scenario, Previously Reported [Member]	Noncontrolling Interest Restatement Adjustment [Member]	Noncontrolling Interest	Scenario, Previously Reported [Member]	Restatement Adjustment [Member]	Total
Beginning balance at Dec. 31, 2015			$ 3,737,986			$ 18,740			$ 4,609,474			$ 1,372,522			$ (2,254,038)			$ (8,712)			$ 362,879			$ 4,100,865
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Grant of restricted stock to company directors (18 shares at $33.09 per share, 32 shares at $31.23 per share and 35 shares at $30.51 per share for 2016, 2017 and 2018 respectively)						2			(2)
Stock-based compensation expense			13,790						13,790															13,790
Vesting/exercising of equity compensation plan, net of tax withholdings (773 shares, 116 shares and 89 shares for 2016, 2017 and 2018 respectively)			(23,426)			77			(23,503)															(23,426)
Dividend reinvestment plan (7,215 shares at $33.27 per share, 1,199 shares at $30.64 per share and 1,549 shares at an average of $30.22 per share for 2016, 2017 and 2018 respectively)			240,041			721			239,320															240,041
Grant of stock as payment of directors fees (10 shares at an average of $31.27 per share and 5 shares at an average of $32.18 per share for 2016 and 2017 respectively)			325			1			324															325
Deferred compensation directors (8 shares at $32.10 per share and 35 shares at $30.42 per share for 2017 and 2018 respectively)			(129)						(129)															(129)
Equity Shelf Program (656 shares at $29.97 per share and 718 shares at $30.81 per share and 2,276 shares at $33.18 per share, net of issuance costs			19,651			66			19,585															19,651
Common dividends declared ($2.36 per share, $2.54 per share and $2.64 per share for 2016, 2017 and 2018 respectively)			(453,349)												(453,349)									(453,349)
Conversion of Omega OP Units to common stock (72 shares at $35.68 per share, 89 shares at $32.91 per share and 53 share at $32.98 per share for 2016, 2017 and 2018 respectively)			2,566			7			2,559															2,566
Redemption of Omega OP Units (94 units, 90 units and 58 units for 2016, 2017 and 2018 respectively)			(10)						(10)												(3,289)			(3,299)
Omega OP Units distributions																					(21,179)			(21,179)
Comprehensive income:
Foreign currency translation			(44,468)															(44,468)			(2,067)			(46,535)
Cash flow hedges			(647)															(647)			(55)			(702)
Net income			366,415									366,415									16,952			383,367
Total comprehensive income																								336,130
Balance , ending at Dec. 31, 2016			3,858,745			19,614			4,861,408			1,738,937			(2,707,387)			(53,827)			353,241			4,211,986
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Grant of restricted stock to company directors (18 shares at $33.09 per share, 32 shares at $31.23 per share and 35 shares at $30.51 per share for 2016, 2017 and 2018 respectively)						3			(3)
Stock-based compensation expense			15,212						15,212															15,212
Vesting/exercising of equity compensation plan, net of tax withholdings (773 shares, 116 shares and 89 shares for 2016, 2017 and 2018 respectively)			(2,143)			12			(2,155)															(2,143)
Dividend reinvestment plan (7,215 shares at $33.27 per share, 1,199 shares at $30.64 per share and 1,549 shares at an average of $30.22 per share for 2016, 2017 and 2018 respectively)			36,722			120			36,602															36,722
Grant of stock as payment of directors fees (10 shares at an average of $31.27 per share and 5 shares at an average of $32.18 per share for 2016 and 2017 respectively)			150			1			149															150
Deferred compensation directors (8 shares at $32.10 per share and 35 shares at $30.42 per share for 2017 and 2018 respectively)			108						108															108
Equity Shelf Program (656 shares at $29.97 per share and 718 shares at $30.81 per share and 2,276 shares at $33.18 per share, net of issuance costs			22,120			72			22,048															22,120
Common dividends declared ($2.36 per share, $2.54 per share and $2.64 per share for 2016, 2017 and 2018 respectively)			(502,861)												(502,861)									(502,861)
Conversion of Omega OP Units to common stock (72 shares at $35.68 per share, 89 shares at $32.91 per share and 53 share at $32.98 per share for 2016, 2017 and 2018 respectively)			2,942			9			2,933															2,942
Redemption of Omega OP Units (94 units, 90 units and 58 units for 2016, 2017 and 2018 respectively)																					(2,990)			(2,990)
Omega OP Units distributions																					(22,626)			(22,626)
Comprehensive income:
Foreign currency translation			20,916															20,916			929			21,845
Cash flow hedges			2,761															2,761			122			2,883
Net income			100,419									100,419									4,491			104,910
Total comprehensive income																								129,638
Balance , ending at Dec. 31, 2017	$ 3,555,091	$ 3,564,668		$ 19,831	$ 19,831		$ 4,936,302	$ 4,936,302		$ 1,839,356	$ 1,848,933		$ (3,210,248)	$ (3,210,248)		$ (30,150)	$ (30,150)		$ 333,167	$ 333,590		$ 3,888,258	$ 3,898,258	3,888,258
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change (see Note 2)		$ 9,577									$ 9,577									$ 423			$ 10,000
Grant of restricted stock to company directors (18 shares at $33.09 per share, 32 shares at $31.23 per share and 35 shares at $30.51 per share for 2016, 2017 and 2018 respectively)						4			(4)
Stock-based compensation expense			15,987						15,987															15,987
Vesting/exercising of equity compensation plan, net of tax withholdings (773 shares, 116 shares and 89 shares for 2016, 2017 and 2018 respectively)			(1,654)			9			(1,663)															(1,654)
Dividend reinvestment plan (7,215 shares at $33.27 per share, 1,199 shares at $30.64 per share and 1,549 shares at an average of $30.22 per share for 2016, 2017 and 2018 respectively)			46,801			155			46,646															46,801
Deferred compensation directors (8 shares at $32.10 per share and 35 shares at $30.42 per share for 2017 and 2018 respectively)			253			3			250															253
Equity Shelf Program (656 shares at $29.97 per share and 718 shares at $30.81 per share and 2,276 shares at $33.18 per share, net of issuance costs			75,532			228			75,304															75,532
Common dividends declared ($2.36 per share, $2.54 per share and $2.64 per share for 2016, 2017 and 2018 respectively)			(528,949)												(528,949)									(528,949)
Conversion of Omega OP Units to common stock (72 shares at $35.68 per share, 89 shares at $32.91 per share and 53 share at $32.98 per share for 2016, 2017 and 2018 respectively)			1,727			5			1,722															1,727
Redemption of Omega OP Units (94 units, 90 units and 58 units for 2016, 2017 and 2018 respectively)																					(1,861)			(1,861)
Omega OP Units distributions																					(23,493)			(23,493)
Comprehensive income:
Foreign currency translation			(13,924)															(13,924)			(608)			(14,532)
Cash flow hedges			2,422															2,422			109			2,531
Net income			281,578									281,578									12,306			293,884
Total comprehensive income																								281,883
Balance , ending at Dec. 31, 2018			$ 3,444,441			$ 20,235			$ 5,074,544			$ 2,130,511			$ (3,739,197)			$ (41,652)			$ 320,043			$ 3,764,484