Segment Reporting (Schedule of Information for Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Rental and parking expenses	$ (7,373)	$ (7,099)	$ (14,012)	$ (14,683)
Income from operations	26,087	22,745	52,588	42,163
Real estate-related notes receivable interest income	15	216	31	355
General and administrative expenses	(1,587)	(1,451)	(3,168)	(2,860)
Change in fair value of contingent consideration	(125)	(150)	(245)	(300)
Acquisition related expenses	(1,640)	(509)	(1,640)	(3,654)
Asset management fees	(4,877)	(4,533)	(9,664)	(8,566)
Depreciation and amortization	(17,349)	(16,445)	(34,348)	(32,228)
Other interest and dividend income	2,706	2,603	5,411	3,119
Interest expense, net	(9,213)	(7,004)	(19,827)	(13,310)
Provision for loan losses	(1,666)	0	(1,666)	0
Net income	17,914	18,344	36,506	31,972
Operating Segments [Member]
Segment Reporting Information [Line Items]
Rental, parking and tenant reimbursement revenue	59,023	52,716	115,634	104,099
Rental and parking expenses	(7,373)	(7,099)	(14,012)	(14,683)
Income from operations	51,650	45,617	101,622	89,416
Operating Segments [Member] | Data Centers [Member]
Segment Reporting Information [Line Items]
Rental, parking and tenant reimbursement revenue	28,971	28,706	57,633	57,819
Rental and parking expenses	(4,936)	(5,380)	(9,759)	(10,440)
Income from operations	24,035	23,326	47,874	47,379
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Rental, parking and tenant reimbursement revenue	30,052	24,010	58,001	46,280
Rental and parking expenses	(2,437)	(1,719)	(4,253)	(4,243)
Income from operations	$ 27,615	$ 22,291	$ 53,748	$ 42,037