Investment in Real Estate (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment in Real Estate
Land	$ 74,819	$ 78,983
Buildings and Improvements	1,024,778	888,966
Construction in progress	126,117	$ 178,599
Total investments in real estate	1,225,714
SV1 San Jose CA
Investment in Real Estate
Land	6,863
Buildings and Improvements	127,238
Construction in progress	664
Total investments in real estate	134,765
SV2 Milpitas CA
Investment in Real Estate
Land	5,086
Buildings and Improvements	26,838
Construction in progress	686
Total investments in real estate	32,610
SV3 Santa Clara CA
Investment in Real Estate
Land	3,972
Buildings and Improvements	49,262
Construction in progress	774
Total investments in real estate	54,008
SV4 Santa Clara CA
Investment in Real Estate
Land	4,501
Buildings and Improvements	91,807
Construction in progress	1,120
Total investments in real estate	97,428
SV5 Santa Clara CA
Investment in Real Estate
Land	2,544
Buildings and Improvements	23,514
Total investments in real estate	26,058
SV6 Santa Clara CA
Investment in Real Estate
Construction in progress	23,009
Total investments in real estate	23,009
SV7 Santa Clara CA
Investment in Real Estate
Construction in progress	10,609
Total investments in real estate	10,609
BO1 Somerville MA
Investment in Real Estate
Land	5,154
Buildings and Improvements	82,181
Construction in progress	3,066
Total investments in real estate	90,401
NY1 New York NY
Investment in Real Estate
Buildings and Improvements	34,432
Construction in progress	185
Total investments in real estate	34,617
NY2 Secaucus NJ
Investment in Real Estate
Land	2,388
Buildings and Improvements	90,346
Construction in progress	36,748
Total investments in real estate	129,482
VA1 Reston VA
Investment in Real Estate
Land	6,903
Buildings and Improvements	115,567
Construction in progress	4,213
Total investments in real estate	126,683
VA2 Reston VA
Investment in Real Estate
Land	2,720
Buildings and Improvements	63,547
Construction in progress	39,446
Total investments in real estate	105,713
DC1 Washington DC
Investment in Real Estate
Buildings and Improvements	8,020
Construction in progress	159
Total investments in real estate	8,179
CH1 Chicago IL
Investment in Real Estate
Land	5,493
Buildings and Improvements	93,326
Construction in progress	848
Total investments in real estate	99,667
LA1 Los Angeles CA
Investment in Real Estate
Buildings and Improvements	64,630
Construction in progress	3,100
Total investments in real estate	67,730
LA2 Los Angeles CA
Investment in Real Estate
Land	28,467
Buildings and Improvements	139,760
Construction in progress	1,232
Total investments in real estate	169,459
MI1 Miami FL
Investment in Real Estate
Land	728
Buildings and Improvements	10,355
Total investments in real estate	11,083
DE1 Denver CO
Investment in Real Estate
Buildings and Improvements	2,903
Construction in progress	249
Total investments in real estate	3,152
DE2 Denver CO
Investment in Real Estate
Buildings and Improvements	1,052
Construction in progress	9
Total investments in real estate	$ 1,061