Discontinued Operations - Summarized Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains (Losses) on Sales of Investment Real Estate		$ 4,075		$ 4,075
Total revenues	$ 167,411	106,102	$ 518,220	322,904
Real estate taxes	18,824	12,072	55,363	37,402
Other operating expenses	30,376	21,785	90,204	66,221
Depreciation and amortization	74,939	42,569	226,373	129,444
Business Combination, Acquisition Related Costs	0	3,813	682	3,813
General and administrative	7,990	22,383	25,457	36,438
Loss on impairment of real estate assets	8,521	0	14,105	5,800
Total expenses	150,168	110,405	438,553	299,608
Dividend income	0	304	1,960	912
Unrealized gain on equity securities	0	17,425	(44,007)	40,677
Interest income	358	140	847	405
Interest expense	(32,367)	(23,374)	(104,848)	(69,444)
Loss on early extinguishment of debt	(284)	0	(769)	0
Income before income tax expense and equity in earnings of an investee	(3,587)	(9,808)	(33,612)	13,175
Income tax expense	(156)	(9)	(509)	(124)
Equity in earnings of an investee	(196)	94	(573)	(1,112)
Net income attributed to SIR	$ (3,939)	$ (449)	$ (34,694)	$ 35,811
Weighted average common shares outstanding (basic) (in shares)	48,073	24,768	48,051	24,764
Weighted average common shares outstanding (diluted) (in shares)	48,073	24,768	48,051	24,769
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)	$ (0.08)	$ (0.02)	$ (0.72)	$ 1.43
SIR | SIR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income		$ 101,833		$ 298,003
Tenant reimbursements and other income		20,048		60,514
Total revenues		121,881		358,517
Real estate taxes		12,518		36,748
Other operating expenses		14,814		43,714
Depreciation and amortization		35,371		105,326
Business Combination, Acquisition Related Costs		3,796		3,796
General and administrative		15,331		47,353
Write-off of straight line rent receivable, net		0		10,626
Loss on impairment of real estate assets		9,706		9,706
Total expenses		91,536		257,269
Dividend income		397		1,190
Unrealized gain on equity securities		22,771		53,159
Interest income		133		753
Interest expense		(23,287)		(69,446)
Loss on early extinguishment of debt		0		(1,192)
Income before income tax expense and equity in earnings of an investee		34,434		89,787
Income tax expense		(185)		(446)
Equity in earnings of an investee		831		882
Net income		35,080		90,223
Net income allocated to noncontrolling interest		(5,597)		(15,841)
Net income attributed to SIR		$ 29,483		$ 74,382
Weighted average common shares outstanding (basic) (in shares)		89,410		89,395
Weighted average common shares outstanding (diluted) (in shares)		89,437		89,411
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)		$ 0.33		$ 0.83