Real Estate Assets and Construction in Progress (Summary of Owned or Leased Properties by the Company) (Details) $ in Thousands	Jun. 30, 2019 USD ($) facility	Dec. 31, 2018 USD ($) facility
Real Estate Properties [Line Items]
Land	$ 107,307	$ 105,541
Buildings, Improvements and Equipment	2,087,374	1,917,251
Construction in progress	856,005	790,064
Total cost	3,050,686	2,812,856
Manassas, Virginia | Assets Held For Sale
Real Estate Properties [Line Items]
Construction in progress		71,000
Owned Properties | Atlanta, Georgia (Atlanta-Metro)
Real Estate Properties [Line Items]
Land	20,416	20,416
Buildings, Improvements and Equipment	498,603	493,446
Construction in progress	129,605	88,253
Total cost	648,624	602,115
Owned Properties | Irving Texas
Real Estate Properties [Line Items]
Land	8,606	8,606
Buildings, Improvements and Equipment	347,082	345,615
Construction in progress	108,093	99,445
Total cost	463,781	453,666
Owned Properties | Richmond, Virginia
Real Estate Properties [Line Items]
Land	2,180	2,180
Buildings, Improvements and Equipment	254,396	253,098
Construction in progress	69,531	67,932
Total cost	326,107	323,210
Owned Properties | Chicago, Illinois
Real Estate Properties [Line Items]
Land	9,400	9,400
Buildings, Improvements and Equipment	153,540	130,150
Construction in progress	129,380	133,095
Total cost	292,320	272,645
Owned Properties | Suwanee, Georgia (Atlanta-Suwanee)
Real Estate Properties [Line Items]
Land	3,521	3,521
Buildings, Improvements and Equipment	170,328	166,298
Construction in progress	1,834	3,188
Total cost	175,683	173,007
Owned Properties | Ashburn, Virginia
Real Estate Properties [Line Items]
Land	17,326	17,325
Buildings, Improvements and Equipment	99,987	63,245
Construction in progress	168,573	184,951
Total cost	285,886	265,521
Owned Properties | Piscataway New Jersey
Real Estate Properties [Line Items]
Land	7,466	7,466
Buildings, Improvements and Equipment	98,665	97,806
Construction in progress	36,146	33,472
Total cost	142,277	138,744
Owned Properties | Santa Clara, California
Real Estate Properties [Line Items]
Buildings, Improvements and Equipment	105,722	98,548
Construction in progress	3,693	7,600
Total cost	109,415	106,148
Owned Properties | Dulles, Virginia
Real Estate Properties [Line Items]
Land	3,154	3,154
Buildings, Improvements and Equipment	73,220	72,435
Construction in progress	4,160	3,852
Total cost	80,534	79,441
Owned Properties | Sacramento, California
Real Estate Properties [Line Items]
Land	1,481	1,481
Buildings, Improvements and Equipment	64,928	64,874
Construction in progress	90	92
Total cost	66,499	66,447
Owned Properties | Fort Worth, Texas
Real Estate Properties [Line Items]
Land	9,079	9,079
Buildings, Improvements and Equipment	44,458	18,623
Construction in progress	30,036	43,715
Total cost	83,573	71,417
Owned Properties | Princeton, New Jersey
Real Estate Properties [Line Items]
Land	20,700	20,700
Buildings, Improvements and Equipment	34,292	34,046
Construction in progress	423	431
Total cost	55,415	55,177
Owned Properties | Groningen, Netherlands
Real Estate Properties [Line Items]
Land	1,766
Buildings, Improvements and Equipment	8,745
Construction in progress	2,634
Total cost	13,145
Owned Properties | Eemshaven, Netherlands
Real Estate Properties [Line Items]
Construction in progress	29,292
Total cost	29,292
Owned Properties | Phoenix, Arizona
Real Estate Properties [Line Items]
Buildings, Improvements and Equipment	73
Construction in progress	30,279	29,562
Total cost	30,352	29,562
Owned Properties | Hillsboro, Oregon
Real Estate Properties [Line Items]
Buildings, Improvements and Equipment	55
Construction in progress	52,642	39,835
Total cost	52,697	39,835
Owned Properties | Manassas, Virginia
Real Estate Properties [Line Items]
Buildings, Improvements and Equipment	0
Construction in progress	58,026	45,194
Total cost	58,026	45,194
Owned Properties | Other
Real Estate Properties [Line Items]
Land	2,212	2,213
Buildings, Improvements and Equipment	35,846	35,720
Construction in progress	46	113
Total cost	$ 38,104	$ 38,046
Leased Properties
Real Estate Properties [Line Items]
Number of facilities leased | facility	9	10
Leased Properties | Owned Properties
Real Estate Properties [Line Items]
Buildings, Improvements and Equipment	$ 97,434	$ 43,347
Construction in progress	1,522	9,334
Total cost	$ 98,956	$ 52,681