Consolidated Statement of Changes in Partner Capital Statement - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income (loss)	$ 19,574	$ 52,690	$ (5,209)	$ 144,183
Other comprehensive loss
Amounts reclassified from accumulated other comprehensive loss	2,484	584	3,909	408
Contributions from partners	31	1,001	131	1,896
Issuance of exchangeable operating partnership units			1,275
Distributions to partners	(654)	(1,299)	(1,818)	(2,864)
Reallocation of limited partner's interest				0
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	3,828	3,952	7,592	7,904
Partners Capital Total [Member]
Net income (loss)	19,046	51,728	(6,286)	142,174
Other comprehensive loss
Amounts reclassified from accumulated other comprehensive loss	2,412	607	3,816	455
Reallocation of limited partner's interest				66
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	3,828	3,952	7,592	7,904
Partnership Interest [Member]
Beginning Balance	6,275,235	6,402,773	6,289,961	6,450,168
Net income (loss)	19,574	52,690	(5,209)	144,183
Other comprehensive loss
Other comprehensive loss before reclassification	(2,131)	(9,104)	(18,195)	(14,456)
Amounts reclassified from accumulated other comprehensive loss	2,484	584	3,909	408
Contributions from partners	31	1,001	131	1,896
Issuance of exchangeable operating partnership units			1,275
Distributions to partners	(102,051)	(99,499)	(203,458)	(199,260)
Reallocation of limited partner's interest		0		0
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	3,828	3,952	7,592	7,904
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				(32,778)
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	(158)		125,615
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	390	451	(4,419)	(5,217)
Ending Balance	6,197,202	6,352,848	6,197,202	6,352,848
Partnership Interest [Member] | Partners Capital Total [Member]
Beginning Balance	6,236,166	6,361,336	6,249,448	6,408,636
Net income (loss)	19,133	51,837	(6,314)	142,473
Other comprehensive loss
Other comprehensive loss before reclassification	(2,026)	(8,616)	(17,031)	(13,643)
Amounts reclassified from accumulated other comprehensive loss	2,423	609	3,833	456
Contributions from partners	0	0	0	0
Issuance of exchangeable operating partnership units			1,275
Distributions to partners	(101,397)	(98,200)	(201,640)	(196,396)
Reallocation of limited partner's interest		0		(66)
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	3,828	3,952	7,592	7,904
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				(32,778)
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	(158)		125,615
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	390	451	(4,419)	(5,217)
Ending Balance	6,158,359	6,311,369	6,158,359	6,311,369
Partnership Interest [Member] | AOCI Attributable to Parent [Member]
Beginning Balance	(25,531)	(6,096)	(11,997)	(927)
Net income (loss)	0	0	0	0
Other comprehensive loss
Other comprehensive loss before reclassification	(2,016)	(8,597)	(16,954)	(13,614)
Amounts reclassified from accumulated other comprehensive loss	2,412	607	3,816	455
Contributions from partners	0	0	0	0
Issuance of exchangeable operating partnership units			0
Distributions to partners	0	0	0	0
Reallocation of limited partner's interest		0		0
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	0	0	0	0
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				0
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	0		0
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	0	0	0	0
Ending Balance	(25,135)	(14,086)	(25,135)	(14,086)
Partnership Interest [Member] | Noncontrolling Interest [Member]
Beginning Balance	39,069	41,437	40,513	41,532
Net income (loss)	441	853	1,105	1,710
Other comprehensive loss
Other comprehensive loss before reclassification	(105)	(488)	(1,164)	(813)
Amounts reclassified from accumulated other comprehensive loss	61	(25)	76	(48)
Contributions from partners	31	1,001	131	1,896
Issuance of exchangeable operating partnership units			0
Distributions to partners	(654)	(1,299)	(1,818)	(2,864)
Reallocation of limited partner's interest		0		66
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	0	0	0	0
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				0
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	0		0
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	0	0	0	0
Ending Balance	38,843	41,479	38,843	41,479
Partnership Interest [Member] | General Partner [Member]
Beginning Balance	6,224,953	6,356,791	6,225,345	6,398,897
Net income (loss)	19,046	51,728	(6,286)	142,174
Other comprehensive loss
Other comprehensive loss before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Contributions from partners	0	0	0	0
Issuance of exchangeable operating partnership units			0
Distributions to partners	(100,941)	(97,995)	(200,729)	(195,987)
Reallocation of limited partner's interest		0		(66)
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	3,828	3,952	7,592	7,904
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				(32,778)
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	(158)		125,615
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	390	451	(4,419)	(5,217)
Ending Balance	6,147,118	6,314,927	6,147,118	6,314,927
Partnership Interest [Member] | Limited Partner [Member]
Beginning Balance	36,744	10,641	36,100	10,666
Net income (loss)	87	109	(28)	299
Other comprehensive loss
Other comprehensive loss before reclassification	(10)	(19)	(77)	(29)
Amounts reclassified from accumulated other comprehensive loss	11	2	17	1
Contributions from partners	0	0	0	0
Issuance of exchangeable operating partnership units			1,275
Distributions to partners	(456)	(205)	(911)	(409)
Reallocation of limited partner's interest		0		0
Restricted units issued as a result of restricted stock issued by Parent Company, net of amortization	0	0	0	0
Common units repurchased and retired as a result of common stock repurchased and retired by Parent Company				0
Common units issued as a result of common stock issued by Parent Company, net of issuance costs	0		0
Common units redeemed as a result of common stock redeemed by Parent Company, net of issuances	0	0	0	0
Ending Balance	$ 36,376	$ 10,528	$ 36,376	$ 10,528