Equity Investment in Select Income REIT - Income Statement Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Rental income	$ 106,102	$ 70,179	$ 322,904	$ 209,362
Real estate taxes	12,072	8,862	37,402	24,980
Other operating expenses	21,785	14,867	66,221	44,046
Depreciation and amortization	42,569	20,781	129,444	61,949
Acquisition and transaction related costs	3,813	0	3,813	0
General and administrative	22,383	3,266	36,438	12,314
Loss on impairment of real estate assets	0	230	5,800	230
Total expenses	110,405	53,414	299,608	157,705
Operating income	(4,303)	16,765	23,296	51,657
Dividend income	304	304	912	911
Unrealized gain on equity securities	17,425	0	40,677	0
Interest income	140	1,715	405	1,843
Interest expense	(23,374)	(16,055)	(69,444)	(43,599)
Loss on early extinguishment of debt	0	(1,715)	0	(1,715)
Income (loss) from continuing operations before income taxes, equity in net earnings (losses) of investees and gain on sale of real estate	(9,808)	1,014	(4,154)	9,097
Income tax expense	(9)	(22)	(124)	(65)
Equity in earnings of an investee	94	31	(1,112)	533
Net income before gain on sale of real estate	(449)	10,989	18,482	30,081
Gain on sale of real estate	0	0	17,329	0
Net income attributed to SIR	$ (449)	$ 10,989	$ 35,811	$ 30,081
Weighted average common shares outstanding (basic) (in shares)	99,071	96,883	99,055	79,778
Weighted average common shares outstanding (diluted) (in shares)	99,071	96,958	99,075	79,852
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)	$ 0.00	$ 0.11	$ 0.36	$ 0.38
SIR
Schedule of Equity Method Investments [Line Items]
Equity in earnings of an investee	$ 9,253	$ 9,453	$ 23,843	$ 20,271
SIR | SIR
Schedule of Equity Method Investments [Line Items]
Rental income	101,833	98,635	298,003	293,020
Tenant reimbursements and other income	20,048	19,379	60,514	57,158
Total revenues	121,881	118,014	358,517	350,178
Real estate taxes	12,518	11,489	36,748	33,168
Other operating expenses	14,814	14,649	43,714	41,039
Depreciation and amortization	35,371	34,713	105,326	102,770
Acquisition and transaction related costs	3,796	0	3,796	0
General and administrative	15,331	1,608	47,353	24,697
Write-off of straight line rents, net	0	0	10,626	12,517
Loss on asset impairment	0	0	0	4,047
Loss on impairment of real estate assets	9,706	0	9,706	229
Total expenses	91,536	62,459	257,269	218,467
Operating income	30,345	55,555	101,248	131,711
Dividend income	397	397	1,190	1,190
Unrealized gain on equity securities	22,771	0	53,159	0
Interest income	133	19	753	39
Interest expense	(23,287)	(24,383)	(69,446)	(68,278)
Loss on early extinguishment of debt	0	0	(1,192)	0
Income (loss) from continuing operations before income taxes, equity in net earnings (losses) of investees and gain on sale of real estate	30,359	31,588	85,712	64,662
Income tax expense	(185)	(177)	(446)	(364)
Equity in earnings of an investee	831	31	882	533
Net income before gain on sale of real estate	31,005	31,442	86,148	64,831
Gain on sale of real estate	4,075	0	4,075	0
Net income	35,080	31,442	90,223	64,831
Net income allocated to noncontrolling interest	(5,597)	0	(15,841)	0
Net income attributed to SIR	$ 29,483	$ 31,442	$ 74,382	$ 64,831
Weighted average common shares outstanding (basic) (in shares)	89,410	89,355	89,395	89,341
Weighted average common shares outstanding (diluted) (in shares)	89,437	89,379	89,411	89,364
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)	$ 0.33	$ 0.35	$ 0.83	$ 0.73