Equity Investment in Select Income REIT - Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Real estate properties, net	$ 1,601,265	$ 1,591,956
Acquired real estate leases, net	118,065	124,848
Cash and cash equivalents	12,808	29,941	$ 15,698	$ 8,785
Rents receivable, net	50,459	48,458
Other assets, net	77,877	68,005
Total assets	2,377,050	2,385,066
Unsecured revolving credit facility	160,000	160,000
Unsecured term loan, net	547,341	547,171
Senior unsecured notes, net	647,213	646,844
Mortgage notes payable, net	27,415	27,837
Assumed real estate lease obligations, net	10,025	10,626
Other liabilities	52,762	54,019
Shareholders' equity	928,570	935,004
Total liabilities and shareholders’ equity	2,377,050	2,385,066
SIR | SIR
Schedule of Equity Method Investments [Line Items]
Real estate properties, net	3,881,945	3,899,792
Acquired real estate leases, net	486,932	506,298
Cash and cash equivalents	18,101	22,127
Rents receivable, net	111,688	124,089
Other assets, net	115,399	87,376
Total assets	4,614,065	4,639,682
Unsecured revolving credit facility	342,000	327,000
Unsecured term loan, net	348,497	348,373
Senior unsecured notes, net	1,431,368	1,430,300
Mortgage notes payable, net	245,418	245,643
Assumed real estate lease obligations, net	75,411	77,622
Other liabilities	120,168	136,782
Shareholders' equity	2,051,203	2,073,962
Total liabilities and shareholders’ equity	$ 4,614,065	$ 4,639,682