Summary of Significant Accounting Policies - Noncontrolling Interests (Details)						3 Months Ended		6 Months Ended
	Jan. 31, 2017 USD ($)	Jan. 12, 2017 USD ($)	Dec. 17, 2015 USD ($) shares	Mar. 01, 2015 USD ($)	Feb. 05, 2015 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) shares	Jun. 30, 2017 USD ($) Rate shares	Dec. 31, 2016 USD ($)	Apr. 01, 2016 USD ($)
Business Acquisition [Line Items]
Purchase price						$ 588,176,000		$ 836,500,000
Percentage of interest held | Rate								96.70%
Operating partnership units redemption ratio								1
Fair value of embedded derivative		$ 5,600,000				$ 0		$ 0	$ 5,571,000
Equity method investment received				$ 5,000,000
Internal rate of return				15.00%
Operating Partnership
Business Acquisition [Line Items]
Purchase price							$ 78,600,000
Units | Operating Partnership
Business Acquisition [Line Items]
Number of units issued for funding purchase price | shares							2,247,817
Supplemental disclosure of noncash activity - issuance of OP Units and Series A Preferred Units in connection with acquisitions							$ 44,300,000
Joint venture, Operating Partnership and Medical Center of New Albany I, LLC
Business Acquisition [Line Items]
Supplemental disclosure of noncash activity - issuance of OP Units and Series A Preferred Units in connection with acquisitions	$ 2,800,000
Payments to acquire businesses, gross	$ 2,100,000
Joint venture, Operating Partnership and Medical Center of New Albany I, LLC | Units | Operating Partnership
Business Acquisition [Line Items]
Decrease from redemptions or purchase of interests (in shares) | shares								38,641
Minnetonka MOB
Business Acquisition [Line Items]
Number of units issued for funding purchase price | shares					44,685
Consideration transferred, equity interests issued and issuable					$ 9,700,000
Minnetonka MOB | Units
Business Acquisition [Line Items]
Preferred shares value redeemed										$ 9,800,000
Fair value of embedded derivative										$ 2,700,000
Nashville MOB
Business Acquisition [Line Items]
Number of units issued for funding purchase price | shares			91,236
Payments to acquire businesses, gross		$ 20,000,000.0
Consideration transferred, equity interests issued and issuable			$ 19,700,000
Series A Preferred Units
Business Acquisition [Line Items]
Cumulative preferred return					5.00%
Redeemable noncontrolling interest, equity, preferred, redemption shares in exchange					1
Redemption value (in dollars per share) | $ / shares					$ 200
Period in which preferred units will be redeemable					1 year