CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Earnings in Excess of Distributions (Distributions in Excess of Earnings)	Accumulated Other Comprehensive Items, Net	Noncontrolling Interests	Redeemable Noncontrolling Interests	Over-Allotment Option [Member]	Over-Allotment Option [Member] Common Stock	Over-Allotment Option [Member] Additional Paid-in Capital	At The Market (ATM) Equity Program [Member]	At The Market (ATM) Equity Program [Member] Common Stock	At The Market (ATM) Equity Program [Member] Additional Paid-in Capital	FORTRUST [Member]	FORTRUST [Member] Common Stock	FORTRUST [Member] Additional Paid-in Capital
Balance (in shares) at Dec. 31, 2016		263,682,670
Balance at Dec. 31, 2016	$ 1,936,671	$ 2,636	$ 3,489,795	$ (1,343,311)	$ (212,573)	$ 124
Increase (Decrease) in Stockholders' Equity
Issuance of shares under employee stock purchase plan and option plans and stock-based compensation (in shares)		1,005,975
Issuance of shares under employee stock purchase plan and option plans and stock-based compensation	29,929	$ 10	29,919
Issuance of shares in connection with Fortrust Transaction (as defined in Note 6 to Notes to Consolidated Financial Statements included in our Annual Report)			(1,505)											$ 83,014	$ 22	$ 82,992
Issuance of shares in connection with Fortrust Transaction (as defined in Note 6 to Notes to Consolidated Financial Statements included in our Annual Report)															2,193,637
Change in value of redeemable noncontrolling interests	(1,505)						$ 1,505
Parent cash dividends declared	(439,327)			(439,327)
Foreign currency translation adjustment	97,123				97,230	(107)
Change in Fair Value of Interest Rate Swap Agreements	0
Net income (loss)	163,953			161,100		2,100
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	163,200
Noncontrolling interests equity contributions	0					0
Noncontrolling interests dividends	(1,956)					(1,956)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	1,497					1,497
Balance at Sep. 30, 2017	$ 1,868,646	$ 2,668	3,601,201	(1,621,538)	(115,343)	1,658
Balance (in shares) at Sep. 30, 2017		266,882,282
Redeemable Noncontrolling Interest at Dec. 31, 2016							54,697
Increase (Decrease) in Temporary Equity [Roll Forward]
Temporary Equity, Foreign Currency Translation Adjustments							(1,260)
Temporary Equity, Net Income							753
Noncontrolling interest equity contributions, redeemable noncontrolling interests							13,230
Temporary Equity, Accretion of Dividends							(1,501)
Redeemable Noncontrolling Interest at Sep. 30, 2017							67,424
Balance (in shares) at Dec. 31, 2017	283,110,183	283,110,183
Balance at Dec. 31, 2017	$ 2,298,842	$ 2,831	4,164,562	(1,765,966)	(103,989)	1,404
Increase (Decrease) in Stockholders' Equity
Issuance of shares under employee stock purchase plan and option plans and stock-based compensation (in shares)		662,389
Issuance of shares under employee stock purchase plan and option plans and stock-based compensation	20,547	$ 7	20,540
Issuance of shares								$ 76,192	$ 22	$ 76,170	$ 8,716	$ 2	$ 8,714
Issuance of shares (in shares)									2,175,000			273,486
Change in value of redeemable noncontrolling interests	(8,799)		(8,799)				8,799
Parent cash dividends declared	(507,437)			(507,437)
Foreign currency translation adjustment	(128,303)				(128,454)	151
Change in Fair Value of Interest Rate Swap Agreements	4,183				4,183
Net income (loss)	205,718
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	205,168			205,233		(65)
Noncontrolling interests dividends	0
Balance at Sep. 30, 2018	$ 1,938,876	$ 2,862	$ 4,261,187	(2,098,403)	$ (228,260)	$ 1,490
Balance (in shares) at Sep. 30, 2018	286,221,058	286,221,058
Redeemable Noncontrolling Interest at Dec. 31, 2017	$ 91,418						91,418
Increase (Decrease) in Temporary Equity [Roll Forward]
Temporary Equity, Foreign Currency Translation Adjustments							(3,987)
Temporary Equity, Net Income							550
Temporary Equity, Accretion of Dividends							(2,035)
Redeemable Noncontrolling Interest at Sep. 30, 2018	94,745						$ 94,745
Increase (Decrease) in Stockholders' Equity
Cumulative-effect adjustment for adoption of ASU 2014-09 (see Note 2.c.) | Accounting Standards Update 2014-09	$ (30,233)			$ (30,233)