Investment in Real Estate (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment in Real Estate
Land	$ 78,983	$ 85,868
Buildings and Improvements	717,007	596,405
Leasehold improvements	95,218	85,907
Construction in progress	157,317	61,328
Total investments in real estate	1,048,525
SV1, San Jose, CA
Investment in Real Estate
Land	6,863
Buildings and Improvements	119,525
Construction in progress	3,693
Total investments in real estate	130,081
SV2, Milpitas, CA
Investment in Real Estate
Land	5,086
Buildings and Improvements	24,202
Construction in progress	484
Total investments in real estate	29,772
SV3, Santa Clara, CA
Investment in Real Estate
Land	3,972
Buildings and Improvements	45,840
Construction in progress	130
Total investments in real estate	49,942
SV4, Santa Clara, CA
Investment in Real Estate
Land	4,442
Buildings and Improvements	86,226
Construction in progress	680
Total investments in real estate	91,348
SV5, Santa Clara, CA
Investment in Real Estate
Land	2,370
Buildings and Improvements	19,986
Total investments in real estate	22,356
Santa Clara Campus, Santa Clara, CA
Investment in Real Estate
Land	8,173
Buildings and Improvements	8,220
Construction in progress	9,384
Total investments in real estate	25,777
BO1, Somerville, MA
Investment in Real Estate
Land	6,100
Buildings and Improvements	77,919
Construction in progress	2,940
Total investments in real estate	86,959
NY1, New York, NY
Investment in Real Estate
Leasehold improvements	32,717
Construction in progress	46
Total investments in real estate	32,763
NY2, Secaucus, NJ
Investment in Real Estate
Land	386
Buildings and Improvements	14,031
Construction in progress	88,905
Total investments in real estate	103,322
VA1, Reston, VA
Investment in Real Estate
Land	6,903
Buildings and Improvements	106,171
Construction in progress	3,121
Total investments in real estate	116,195
VA2, Reston, VA
Investment in Real Estate
Construction in progress	34,030
Total investments in real estate	34,030
DC1, Washington, DC
Investment in Real Estate
Leasehold improvements	7,417
Construction in progress	269
Total investments in real estate	7,686
CH1, Chicago, IL
Investment in Real Estate
Land	5,493
Buildings and Improvements	82,011
Construction in progress	164
Total investments in real estate	87,668
LA1, Los Angeles, CA
Investment in Real Estate
Leasehold improvements	53,669
Construction in progress	2,938
Total investments in real estate	56,607
LA2, Los Angeles, CA
Investment in Real Estate
Land	28,467
Buildings and Improvements	122,912
Construction in progress	10,457
Total investments in real estate	161,836
MI1, Miami, FL
Investment in Real Estate
Land	728
Buildings and Improvements	9,964
Construction in progress	4
Total investments in real estate	10,696
DE1, Denver, CO
Investment in Real Estate
Leasehold improvements	730
Construction in progress	6
Total investments in real estate	736
DE2, Denver, CO
Investment in Real Estate
Leasehold improvements	685
Construction in progress	66
Total investments in real estate	$ 751