Equity Investment in Select Income REIT - Balance Sheet Information (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Real estate properties, net	$ 1,601,940	$ 1,591,956
Acquired real estate leases, net	108,927	124,848
Cash and cash equivalents	12,907	29,941	$ 9,021	$ 8,785
Rents receivable, net	47,717	48,458
Other assets, net	82,256	68,005
Total assets	2,365,109	2,385,066
Unsecured revolving credit facility	155,000	160,000
Unsecured term loan, net	547,511	547,171
Senior unsecured notes, net	647,584	646,844
Mortgage notes payable, net	26,991	27,837
Assumed real estate lease obligations, net	9,423	10,626
Other liabilities	64,479	54,019
Shareholders' equity	908,679	935,004
Total liabilities and shareholders’ equity	2,365,109	2,385,066
SIR | SIR
Schedule of Equity Method Investments [Line Items]
Real estate properties, net	3,892,729	3,899,792
Acquired real estate leases, net	496,792	506,298
Properties held for sale	23,089	0
Cash and cash equivalents	21,683	22,127
Rents receivable, net	114,430	124,089
Other assets, net	124,867	87,376
Total assets	4,673,590	4,639,682
Unsecured revolving credit facility	67,000	327,000
Unsecured term loan, net	348,622	348,373
Senior unsecured notes, net	1,774,769	1,430,300
Mortgage notes payable, net	245,235	245,643
Assumed real estate lease obligations, net	73,200	77,622
Other liabilities	133,510	136,782
Shareholders' equity	2,031,254	2,073,962
Total liabilities and shareholders’ equity	$ 4,673,590	$ 4,639,682