Property Investments (Details) $ in Thousands	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($)
Summary of Company's investment
Number of facilities | property	201
Number of real estate investments | property	201
Land	$ 221,406
Buildings, Improvements,and Lease Intangibles	3,601,460	$ 3,386,480
Buildings, Improvements, and Lease Intangibles, including Construction in Progress	3,606,918
Personal Property	10,314	10,291
Total real estate properties	3,838,638	3,628,221
Accumulated Depreciation	(897,430)	$ (840,839)
Total real estate investments	3,838,638
Wholly Owned Properties [Member]
Summary of Company's investment
Accumulated Depreciation	$ (897,430)
Land Held for Development and Corporate Property [Member]
Summary of Company's investment
Number of facilities | property	0
Land	$ 20,123
Buildings, Improvements,and Lease Intangibles	5,458
Personal Property	5,603
Total real estate properties	31,184
Accumulated Depreciation	$ (4,640)
Land Held for Development [Member]
Summary of Company's investment
Number of facilities | property	0
Land	$ 20,123
Buildings, Improvements,and Lease Intangibles	0
Personal Property	0
Total real estate properties	20,123
Accumulated Depreciation	(239)
Construction in Progress [Member]
Summary of Company's investment
Buildings, Improvements,and Lease Intangibles	5,458
Total real estate properties	$ 5,458
Corporate Property [Member]
Summary of Company's investment
Number of facilities | property	0
Land	$ 0
Buildings, Improvements,and Lease Intangibles	0
Personal Property	5,603
Total real estate properties	5,603
Accumulated Depreciation	$ (4,401)
Medical office/outpatient [Member]
Summary of Company's investment
Number of facilities | property	188
Land	$ 192,304
Buildings, Improvements,and Lease Intangibles	3,290,061
Personal Property	4,113
Total real estate properties	3,486,478
Accumulated Depreciation	$ (816,432)
Medical office/outpatient [Member] | Colorado [Member]
Summary of Company's investment
Number of facilities | property	6
Land	$ 4,086
Buildings, Improvements,and Lease Intangibles	122,689
Personal Property	271
Total real estate properties	127,046
Accumulated Depreciation	$ (18,736)
Medical office/outpatient [Member] | DISTRICT OF COLUMBIA
Summary of Company's investment
Number of facilities | property	4
Land	$ 0
Buildings, Improvements,and Lease Intangibles	100,570
Personal Property	0
Total real estate properties	100,570
Accumulated Depreciation	$ (15,826)
Medical office/outpatient [Member] | Georgia [Member]
Summary of Company's investment
Number of facilities | property	8
Land	$ 1,015
Buildings, Improvements,and Lease Intangibles	187,042
Personal Property	0
Total real estate properties	188,057
Accumulated Depreciation	$ (1,203)
Medical office/outpatient [Member] | Austin, Texas [Member]
Summary of Company's investment
Number of facilities | property	4
Land	$ 12,756
Buildings, Improvements,and Lease Intangibles	85,961
Personal Property	105
Total real estate properties	98,822
Accumulated Depreciation	$ (17,498)
Medical office/outpatient [Member] | Hawaii [Member]
Summary of Company's investment
Number of facilities | property	3
Land	$ 8,327
Buildings, Improvements,and Lease Intangibles	132,847
Personal Property	159
Total real estate properties	141,333
Accumulated Depreciation	$ (30,066)
Medical office/outpatient [Member] | Illinois [Member]
Summary of Company's investment
Number of facilities | property	3
Land	$ 5,859
Buildings, Improvements,and Lease Intangibles	79,295
Personal Property	200
Total real estate properties	85,354
Accumulated Depreciation	$ (15,476)
Medical office/outpatient [Member] | Dallas, Texas [Member]
Summary of Company's investment
Number of facilities | property	24
Land	$ 12,472
Buildings, Improvements,and Lease Intangibles	365,657
Personal Property	416
Total real estate properties	378,545
Accumulated Depreciation	$ (128,557)
Medical office/outpatient [Member] | Indiana [Member]
Summary of Company's investment
Number of facilities | property	3
Land	$ 3,299
Buildings, Improvements,and Lease Intangibles	71,641
Personal Property	0
Total real estate properties	74,940
Accumulated Depreciation	$ (18,742)
Medical office/outpatient [Member] | Memphis, Tennessee [Member]
Summary of Company's investment
Number of facilities | property	7
Land	$ 5,241
Buildings, Improvements,and Lease Intangibles	88,517
Personal Property	160
Total real estate properties	93,918
Accumulated Depreciation	$ (31,675)
Medical office/outpatient [Member] | Nashville, Tennessee [Member]
Summary of Company's investment
Number of facilities | property	5
Land	$ 3,143
Buildings, Improvements,and Lease Intangibles	149,859
Personal Property	278
Total real estate properties	153,280
Accumulated Depreciation	$ (43,000)
Medical office/outpatient [Member] | Iowa [Member]
Summary of Company's investment
Number of facilities | property	6
Land	$ 12,665
Buildings, Improvements,and Lease Intangibles	79,214
Personal Property	94
Total real estate properties	91,973
Accumulated Depreciation	$ (18,263)
Medical office/outpatient [Member] | North Carolina [Member]
Summary of Company's investment
Number of facilities | property	16
Land	$ 4,200
Buildings, Improvements,and Lease Intangibles	163,603
Personal Property	95
Total real estate properties	167,898
Accumulated Depreciation	$ (56,355)
Medical office/outpatient [Member] | Oklahoma [Member]
Summary of Company's investment
Number of facilities | property	2
Land	$ 7,673
Buildings, Improvements,and Lease Intangibles	101,432
Personal Property	6
Total real estate properties	109,111
Accumulated Depreciation	$ (10,890)
Medical office/outpatient [Member] | Los Angeles, California [Member]
Summary of Company's investment
Number of facilities | property	11
Land	$ 27,709
Buildings, Improvements,and Lease Intangibles	141,681
Personal Property	277
Total real estate properties	169,667
Accumulated Depreciation	$ (71,808)
Medical office/outpatient [Member] | Virginia [Member]
Summary of Company's investment
Number of facilities | property	7
Land	$ 0
Buildings, Improvements,and Lease Intangibles	146,176
Personal Property	98
Total real estate properties	146,274
Accumulated Depreciation	$ (32,299)
Medical office/outpatient [Member] | San Antonio, Texas [Member]
Summary of Company's investment
Number of facilities | property	7
Land	$ 6,647
Buildings, Improvements,and Lease Intangibles	88,129
Personal Property	370
Total real estate properties	95,146
Accumulated Depreciation	$ (34,514)
Medical office/outpatient [Member] | San Francisco, California [Member]
Summary of Company's investment
Number of facilities | property	3
Land	$ 14,054
Buildings, Improvements,and Lease Intangibles	103,938
Personal Property	43
Total real estate properties	118,035
Accumulated Depreciation	$ (12,223)
Medical office/outpatient [Member] | Washington [Member]
Summary of Company's investment
Number of facilities | property	17
Land	$ 24,560
Buildings, Improvements,and Lease Intangibles	403,614
Personal Property	378
Total real estate properties	428,552
Accumulated Depreciation	$ (52,457)
Medical office/outpatient [Member] | Other (22 MSAs) [Member]
Summary of Company's investment
Number of facilities | property	52
Land	$ 38,598
Buildings, Improvements,and Lease Intangibles	678,196
Personal Property	1,163
Total real estate properties	717,957
Accumulated Depreciation	$ (206,844)
Inpatient [Member]
Summary of Company's investment
Number of facilities | property	5
Land	$ 7,054
Buildings, Improvements,and Lease Intangibles	247,125
Personal Property	0
Total real estate properties	254,179
Accumulated Depreciation	$ (56,123)
Inpatient [Member] | Colorado [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 623
Buildings, Improvements,and Lease Intangibles	10,788
Personal Property	0
Total real estate properties	11,411
Accumulated Depreciation	$ (1,781)
Inpatient [Member] | Dallas, Texas [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 4,442
Buildings, Improvements,and Lease Intangibles	92,990
Personal Property	0
Total real estate properties	97,432
Accumulated Depreciation	$ (19,538)
Inpatient [Member] | Missouri [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 1,989
Buildings, Improvements,and Lease Intangibles	109,304
Personal Property	0
Total real estate properties	111,293
Accumulated Depreciation	$ (12,046)
Inpatient [Member] | Los Angeles, California [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 0
Buildings, Improvements,and Lease Intangibles	12,688
Personal Property	0
Total real estate properties	12,688
Accumulated Depreciation	$ (7,606)
Inpatient [Member] | Pennsylvania [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 0
Buildings, Improvements,and Lease Intangibles	21,355
Personal Property	0
Total real estate properties	21,355
Accumulated Depreciation	$ (15,152)
Other [Member]
Summary of Company's investment
Number of facilities | property	8
Land	$ 1,925
Buildings, Improvements,and Lease Intangibles	64,274
Personal Property	598
Total real estate properties	66,797
Accumulated Depreciation	$ (20,235)
Other [Member] | Austin, Texas [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 1,480
Buildings, Improvements,and Lease Intangibles	3,872
Personal Property	2
Total real estate properties	5,354
Accumulated Depreciation	$ (164)
Other [Member] | Fenton, Michigan [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 40
Buildings, Improvements,and Lease Intangibles	3,468
Personal Property	32
Total real estate properties	3,540
Accumulated Depreciation	$ (2,738)
Other [Member] | Ovid, Michigan [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 62
Buildings, Improvements,and Lease Intangibles	3,188
Personal Property	49
Total real estate properties	3,299
Accumulated Depreciation	$ (2,096)
Other [Member] | Fremont, Michigan [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 7
Buildings, Improvements,and Lease Intangibles	3,242
Personal Property	35
Total real estate properties	3,284
Accumulated Depreciation	$ (2,565)
Other [Member] | St. Louis, Michigan [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 31
Buildings, Improvements,and Lease Intangibles	1,735
Personal Property	33
Total real estate properties	1,799
Accumulated Depreciation	$ 1,341
Other [Member] | Iowa [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 0
Buildings, Improvements,and Lease Intangibles	40,354
Personal Property	5
Total real estate properties	40,359
Accumulated Depreciation	$ (7,704)
Other [Member] | Johnson City, Tennessee [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 253
Buildings, Improvements,and Lease Intangibles	7,319
Personal Property	408
Total real estate properties	7,980
Accumulated Depreciation	$ (2,798)
Other [Member] | Detroit, Michigan [Member]
Summary of Company's investment
Number of facilities | property	1
Land	$ 52
Buildings, Improvements,and Lease Intangibles	1,096
Personal Property	34
Total real estate properties	1,182
Accumulated Depreciation	$ (829)