Acquisitions, Dispositions and Mortgage Repayments - Acquisitions (Details) $ in Thousands																						12 Months Ended
	Dec. 18, 2019 USD ($) ft²	Dec. 13, 2019 USD ($) ft²	Dec. 10, 2019 USD ($) ft²	Nov. 18, 2019 USD ($) ft²	Oct. 31, 2019 USD ($) ft²	Sep. 30, 2019 USD ($) ft² property	Sep. 26, 2019 USD ($) ft²	Aug. 01, 2019 USD ($) ft²	Jun. 28, 2019 USD ($) ft²	Jun. 14, 2019 USD ($) ft²	Jun. 11, 2019 USD ($) ft²	Jun. 10, 2019 USD ($) ft²	Apr. 02, 2019 USD ($) ft²	Mar. 28, 2019 USD ($) ft² property Lease	Dec. 19, 2018 USD ($) ft²	Dec. 14, 2018 USD ($) ft²	Aug. 24, 2018 USD ($) ft²	Jun. 29, 2018 USD ($) ft²	May 21, 2018 USD ($) ft²	May 18, 2018 USD ($) ft²	May 04, 2018 USD ($) ft²	Dec. 31, 2019 USD ($) ft² property	Dec. 31, 2018 USD ($) ft² Lease
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Purchase price																						$ 381,300
Cash consideration																						378,500
Real estate																						384,700
Other																						$ (6,200)
Square footage | ft²																						1,086,712
Number of properties subject to ground leases																						108	107
Financing lease liabilities																						$ 18,037
Above-market lease intangibles																						1,200	$ 16,800
Ground leases																						9,400	9,900
2018 Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Purchase price																							111,500
Mortgage notes payable assumed																							(8,000)
Cash consideration																							103,100
Real estate																							112,400
Other																							$ (1,200)
Square footage | ft²																							511,422
Unamortized premium of notes assumed																							$ 100
Medical Office Building [Member] | Washington, D.C. [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired														Mar. 28, 2019
Purchase price														$ 46,000
Cash consideration														45,900
Real estate														50,200
Other														$ (4,300)
Square footage | ft²														158,338
Number of properties acquired | property														2
Number of properties subject to ground leases | Lease														2
Financing lease liabilities																						14,300
Above-market lease intangibles																						$ 5,200
Medical Office Building [Member] | Indiana [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired														Mar. 28, 2019
Purchase price														$ 47,000
Cash consideration														44,800
Real estate														43,700
Other														$ 1,100
Square footage | ft²														143,499
Ground leases														$ 800
Below-market lease intangible														$ 900
Medical Office Building [Member] | Georgia [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired													Apr. 02, 2019
Purchase price													$ 28,000
Cash consideration													28,000
Real estate													28,000
Other													$ 0
Square footage | ft²													47,963
Medical Office Building [Member] | Dallas, Texas [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired					Oct. 31, 2019							Jun. 10, 2019
Purchase price					$ 20,100							$ 17,000
Cash consideration					19,500							16,700
Real estate					20,200							17,000
Other					$ (700)							$ (300)
Square footage | ft²					48,192							89,990
Present value of future lease payments					$ 3,600
Medical Office Building [Member] | Washington [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired	Dec. 18, 2019		Dec. 10, 2019	Nov. 18, 2019					Jun. 28, 2019	Jun. 14, 2019	Jun. 11, 2019
Purchase price	$ 10,000		$ 24,200	$ 22,800					$ 30,500	$ 19,000	$ 7,700
Cash consideration	9,300		24,500	23,100					30,400	19,100	7,800
Real estate	9,900		24,600	23,200					30,600	19,500	7,800
Other	$ (600)		$ (100)	$ (100)					$ (200)	$ (400)	$ 0
Square footage | ft²	20,109		44,166	36,350					78,288	47,255	29,870
Medical Office Building [Member] | Houston, Texas [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired								Aug. 01, 2019
Purchase price								$ 13,500
Cash consideration								13,500
Real estate								13,500
Other								$ 0
Square footage | ft²								29,903
Medical Office Building [Member] | Oklahoma [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired							Sep. 26, 2019
Purchase price							$ 4,100
Cash consideration							4,100
Real estate							4,100
Other							$ 0
Square footage | ft²							28,542
Medical Office Building [Member] | California [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired						Sep. 30, 2019
Purchase price						$ 61,100
Cash consideration						60,900
Real estate						61,800
Other						$ (900)
Square footage | ft²						115,634
Number of properties acquired | property						2
Medical Office Building [Member] | North Carolina [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired					Oct. 31, 2019
Purchase price					$ 21,600
Cash consideration					22,000
Real estate					21,700
Other					$ 300
Square footage | ft²					57,730
Medical Office Building [Member] | Tennessee [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired		Dec. 13, 2019
Purchase price		$ 8,700
Cash consideration		8,900
Real estate		8,900
Other		$ 0
Square footage | ft²		110,883
Medical Office Building [Member] | 2018 Real estate acquisitions [Member] | Washington [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired																		Jun. 29, 2018			May 04, 2018
Purchase price																		$ 26,200			$ 7,800
Mortgage notes payable assumed																		0			0
Cash consideration																		26,200			7,800
Real estate																		26,700			7,800
Other																		$ (500)			$ 0
Square footage | ft²																		86,942			13,314
Medical Office Building [Member] | 2018 Real estate acquisitions [Member] | Colorado [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired																	Aug. 24, 2018			May 18, 2018
Purchase price																	$ 4,100			$ 12,100
Mortgage notes payable assumed																	0			(8,000)
Cash consideration																	4,200			3,800
Real estate																	4,200			12,100
Other																	$ 0			$ (200)
Square footage | ft²																	17,084			93,992
Medical Office Building [Member] | 2018 Real estate acquisitions [Member] | Oklahoma [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired																			May 21, 2018
Purchase price																			$ 11,400
Mortgage notes payable assumed																			0
Cash consideration																			11,400
Real estate																			11,500
Other																			$ (100)
Square footage | ft²																			82,647
Medical Office Building [Member] | 2018 Real estate acquisitions [Member] | Illinois [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired															Dec. 19, 2018
Purchase price															$ 5,100
Mortgage notes payable assumed															0
Cash consideration															4,900
Real estate															5,100
Other															$ (200)
Square footage | ft²															14,883
Office Building [Member] | 2018 Real estate acquisitions [Member] | Colorado [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired																				May 18, 2018
Purchase price																				$ 12,900
Mortgage notes payable assumed																				0
Cash consideration																				12,800
Real estate																				13,000
Other																				$ (200)
Square footage | ft²																				93,869
Office Building [Member] | 2018 Real estate acquisitions [Member] | Tennessee [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Date acquired																Dec. 04, 2018
Purchase price																$ 31,900
Mortgage notes payable assumed																0
Cash consideration																32,000
Real estate																32,000
Other																$ 0
Square footage | ft²																108,691