Discontinued Operations - Summarized Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tenant reimbursements and other income	$ 21,540		$ 43,663
Total revenues	176,032	$ 108,085	350,809	$ 216,802
Real estate taxes	18,147	12,365	36,539	25,330
Other operating expenses	29,692	21,599	59,828	44,436
Depreciation and amortization	73,913	42,671	151,434	86,875
General and administrative	8,744	4,449	17,467	14,055
Total expenses	140,444	86,786	288,385	189,203
Dividend income	980	304	1,960	608
Unrealized gain on equity securities	(66,135)	10,321	(44,007)	23,252
Interest income	241	149	489	265
Interest expense	(35,348)	(23,304)	(72,481)	(46,070)
Loss on early extinguishment of debt	(71)	0	(485)	0
Income before income tax expense and equity in earnings of an investee	(64,762)	26,098	(30,025)	22,983
Income tax benefit (expense)	130	(83)	(353)	(115)
Equity in earnings of an investee	(142)	(629)	(377)	(1,206)
Net income attributed to SIR	$ (64,774)	$ 29,695	$ (30,755)	$ 36,260
Weighted average common shares outstanding (basic) (in shares)	48,049	24,763	48,040	24,762
Weighted average common shares outstanding (diluted) (in shares)	48,049	24,766	48,040	24,763
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)	$ (1.35)	$ 1.20	$ (0.64)	$ 1.45
SIR | SIR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income		$ 96,415		$ 196,170
Tenant reimbursements and other income		19,592		40,466
Total revenues		116,007		236,636
Real estate taxes		12,442		24,230
Other operating expenses		13,618		28,900
Depreciation and amortization		35,009		69,955
General and administrative		18,081		32,022
Write-off of straight line rent receivable, net		10,626		10,626
Total expenses		89,776		165,733
Dividend income		396		793
Unrealized gain on equity securities		13,488		30,388
Interest income		110		620
Interest expense		(22,667)		(46,159)
Loss on early extinguishment of debt		0		(1,192)
Income before income tax expense and equity in earnings of an investee		17,558		55,353
Income tax benefit (expense)		(101)		(261)
Equity in earnings of an investee		7		51
Net income		17,464		55,143
Net income allocated to noncontrolling interest		(5,765)		(10,244)
Net income attributed to SIR		$ 11,699		$ 44,899
Weighted average common shares outstanding (basic) (in shares)		89,393		89,388
Weighted average common shares outstanding (diluted) (in shares)		89,416		89,398
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)		$ 0.13		$ 0.50