Real Estate Assets and Construction in Progress (Summary of Properties Owned or Leased by the Company) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Real Estate Properties [Line Items]
Land	$ 48,577		$ 48,577
Buildings and improvements	954,915		914,286
Construction in progress	266,234		214,719
Total cost	1,269,726		1,177,582
Owned Properties [Member]
Real Estate Properties [Line Items]
Land	48,577		48,577
Buildings and improvements	926,608		886,116
Construction in progress	265,281		213,772
Total cost	1,240,466		1,148,465
Owned Properties [Member] | Suwanee, Georgia (Atlanta-Suwanee) [Member]
Real Estate Properties [Line Items]
Land	3,521		3,521
Buildings and improvements	142,056		138,991
Construction in progress	9,162		6,345
Total cost	154,739		148,857
Owned Properties [Member] | Atlanta, Georgia (Atlanta-Metro) [Member]
Real Estate Properties [Line Items]
Land	15,397		15,397
Buildings and improvements	374,147		356,122
Construction in progress	18,668		22,693
Total cost	408,212		394,212
Owned Properties [Member] | Santa Clara, California [Member]
Real Estate Properties [Line Items]
Land		[1]		[1]
Buildings and improvements	91,151	[1]	90,332	[1]
Construction in progress	742	[1]	650	[1]
Total cost	91,893	[1]	90,982	[1]
Owned Properties [Member] | Richmond, Virginia [Member]
Real Estate Properties [Line Items]
Land	2,180		2,180
Buildings and improvements	127,843		127,080
Construction in progress	112,981		71,794
Total cost	243,004		201,054
Owned Properties [Member] | Sacramento, California [Member]
Real Estate Properties [Line Items]
Land	1,481		1,481
Buildings and improvements	60,158		60,094
Construction in progress	386		278
Total cost	62,025		61,853
Owned Properties [Member] | Princeton New Jersey [Member]
Real Estate Properties [Line Items]
Land	17,976		17,976
Buildings and improvements	35,977		35,951
Construction in progress	220		90
Total cost	54,173		54,017
Owned Properties [Member] | Dallas, Texas [Member]
Real Estate Properties [Line Items]
Land	5,808		5,808
Buildings and improvements	61,551		44,053
Construction in progress	96,134		89,982
Total cost	163,493		139,843
Owned Properties [Member] | Chicago, Illinois [Member]
Real Estate Properties [Line Items]
Land
Buildings and improvements
Construction in progress	26,766		21,786
Total cost	26,766		21,786
Owned Properties [Member] | Miami, Florida [Member]
Real Estate Properties [Line Items]
Land	1,777		1,777
Buildings and improvements	28,850		28,786
Construction in progress	205		129
Total cost	30,832		30,692
Owned Properties [Member] | Lenexa, Kansas [Member]
Real Estate Properties [Line Items]
Land	437		437
Buildings and improvements	3,466		3,298
Construction in progress	17		25
Total cost	3,920		3,760
Owned Properties [Member] | Wichita, Kansas [Member]
Real Estate Properties [Line Items]
Land
Buildings and improvements	1,409		1,409
Construction in progress
Total cost	1,409		1,409
Leased Properties [Member]
Real Estate Properties [Line Items]
Land
Buildings and improvements	28,307		28,170
Construction in progress	953		947
Total cost	29,260		29,117
Leased Properties [Member] | Jersey City, New Jersey [Member]
Real Estate Properties [Line Items]
Land
Buildings and improvements	27,450		27,318
Construction in progress	923		920
Total cost	28,373		28,238
Leased Properties [Member] | Overland Park, Kansas [Member]
Real Estate Properties [Line Items]
Land
Buildings and improvements	857	[2]	852	[2]
Construction in progress	30		27
Total cost	$ 887		$ 879

[1] Owned facility subject to long-term ground sublease.

[2] This does not include the portion of the business that is used for QTS office space or other real estate not used by customers.