CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Rental income	$ 69,887	$ 64,061	$ 139,183	$ 127,672
Expenses:
Real estate taxes	7,941	7,566	16,118	15,219
Utility expenses	4,172	3,673	8,778	7,847
Other operating expenses	15,187	13,266	29,179	26,177
Depreciation and amortization	20,663	17,985	41,168	36,309
Acquisition related costs	0	64	0	216
General and administrative	5,086	4,008	9,048	7,534
Total expenses	53,049	46,562	104,291	93,302
Operating income	16,838	17,499	34,892	34,370
Dividend income	303	363	607	363
Interest income	67	10	128	16
Interest expense (including net amortization of debt premiums and discounts and debt issuance costs of $808, $747, $1,615 and $1,219, respectively)	(13,963)	(10,314)	(27,544)	(19,678)
Gain on early extinguishment of debt	0	0	0	104
Gain on issuance of shares by Select Income REIT	21	16	21	16
Income from continuing operations before income taxes and equity in earnings of investees	3,266	7,574	8,104	15,191
Income tax expense	(25)	(35)	(43)	(50)
Equity in earnings of investees	8,581	9,400	11,320	19,334
Income from continuing operations	11,822	16,939	19,381	34,475
Loss from discontinued operations	(145)	(126)	(289)	(275)
Net income	11,677	16,813	19,092	34,200
Other comprehensive income:
Unrealized gain (loss) on investment in available for sale securities	(1,032)	7,237	11,110	20,108
Equity in unrealized gain (loss) of investees	(332)	2,606	4,283	7,150
Other comprehensive income (loss)	(1,364)	9,843	15,393	27,258
Comprehensive income	$ 10,313	$ 26,656	$ 34,485	$ 61,458
Weighted average common shares outstanding (basic) (in shares)	71,088	71,038	71,083	71,034
Weighted average common shares outstanding (diluted) (in shares)	71,119	71,061	71,109	71,046
Per common share amounts (basic and diluted):
Income from continuing operations (in dollars per share)	$ 0.17	$ 0.24	$ 0.27	$ 0.49
Loss from discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00
Net income (in dollars per share)	$ 0.16	$ 0.24	$ 0.27	$ 0.48