Investment in Real Estate (Details) (USD $)	9 Months Ended						9 Months Ended				0 Months Ended			9 Months Ended
	Sep. 30, 2013 item	Dec. 31, 2012	Sep. 30, 2013 SV1, San Jose, CA	Sep. 30, 2013 SV2, Milpitas, CA	Sep. 30, 2013 SV3, Santa Clara, CA	Sep. 30, 2013 SV4, Santa Clara, CA	Sep. 30, 2013 SV5, Santa Clara, CA	Sep. 30, 2013 Santa Clara Campus, Santa Clara, CA	Sep. 30, 2013 BO1, Somerville, MA	Sep. 30, 2013 NY1, New York, NY	Feb. 07, 2013 NY2, Secaucus, NJ	Sep. 30, 2013 NY2, Secaucus, NJ	Sep. 30, 2013 VA1, Reston, VA	Sep. 30, 2013 VA2, Reston, VA	Sep. 30, 2013 DC1, Washington, DC	Sep. 30, 2013 CH1, Chicago, IL	Sep. 30, 2013 LA1, Los Angeles, CA	Sep. 30, 2013 LA2, Los Angeles, CA	Sep. 30, 2013 MI1, Miami, FL	Sep. 30, 2013 DE1, Denver, CO	Sep. 30, 2013 DE2, Denver, CO
Investment in Real Estate
Real estate value of acquired land and a vacant building											$ 23,000,000
Number of other data center facilities on which development is commenced	2
Reclassification of property							2,400,000							5,200,000
Land	76,227,000	85,868,000	6,863,000	5,086,000	3,972,000	4,442,000		8,173,000	6,100,000				6,903,000			5,493,000		28,467,000	728,000
Buildings and Improvements	668,580,000	596,405,000	114,425,000	23,780,000	45,821,000	85,671,000		8,221,000	77,388,000				105,658,000			75,951,000		121,819,000	9,846,000
Leasehold improvements	92,996,000	85,907,000								32,522,000					7,264,000		51,830,000			711,000	669,000
Construction in progress	157,200,000	61,328,000	4,607,000	271,000	130,000	942,000	21,178,000	9,055,000	2,900,000	180,000		78,563,000	3,487,000	22,227,000	262,000	5,415,000	2,363,000	5,486,000	118,000	15,000	1,000
Total investments in real estate	$ 995,003,000		$ 125,895,000	$ 29,137,000	$ 49,923,000	$ 91,055,000	$ 21,178,000	$ 25,449,000	$ 86,388,000	$ 32,702,000		$ 78,563,000	$ 116,048,000	$ 22,227,000	$ 7,526,000	$ 86,859,000	$ 54,193,000	$ 155,772,000	$ 10,692,000	$ 726,000	$ 670,000