Real Estate Assets and Construction in Progress - Summary of Properties Owned or Leased by the Company (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Real Estate Properties [Line Items]
Land	$ 48,576	$ 30,601
Buildings and improvements	829,057	728,230
Construction in progress	183,516	146,904
Total Cost	1,061,149	905,735
Owned Properties [Member]
Real Estate Properties [Line Items]
Land	48,576	30,601
Buildings and improvements	802,625	703,657
Construction in progress	182,888	146,904
Total Cost	1,034,089	881,162
Owned Properties [Member] | Suwanee, Georgia (Atlanta-Suwanee) [Member]
Real Estate Properties [Line Items]
Land	3,521	3,521
Buildings and improvements	131,966	126,486
Construction in progress	2,468	3,270
Total Cost	137,955	133,277
Owned Properties [Member] | Atlanta, Georgia (Atlanta-Metro) [Member]
Real Estate Properties [Line Items]
Land	15,396	15,397
Buildings and improvements	348,547	296,547
Construction in progress	4,800	32,456
Total Cost	368,743	344,400
Owned Properties [Member] | Santa Clara, California [Member]
Real Estate Properties [Line Items]
Buildings and improvements	88,214	86,544
Construction in progress	953	1,249
Total Cost	89,167	87,793
Owned Properties [Member] | Richmond, Virginia [Member]
Real Estate Properties [Line Items]
Land	2,180	2,180
Buildings and improvements	112,762	108,979
Construction in progress	72,266	67,155
Total Cost	187,208	178,314
Owned Properties [Member] | Sacramento, California [Member]
Real Estate Properties [Line Items]
Land	1,481	1,481
Buildings and improvements	53,079	52,841
Construction in progress	5,411	4,273
Total Cost	59,971	58,595
Owned Properties [Member] | Princeton New Jersey [Member]
Real Estate Properties [Line Items]
Land	17,976
Buildings and improvements	35,865
Total Cost	53,841
Owned Properties [Member] | Dallas, Texas [Member]
Real Estate Properties [Line Items]
Land	5,808	5,808
Construction in progress	96,928	38,501
Total Cost	102,736	44,309
Owned Properties [Member] | Miami, Florida [Member]
Real Estate Properties [Line Items]
Land	1,777	1,777
Buildings and improvements	27,656	27,553
Construction in progress	62
Total Cost	29,495	29,330
Owned Properties [Member] | Lenexa, Kansas [Member]
Real Estate Properties [Line Items]
Land	437	437
Buildings and improvements	3,127	3,298
Total Cost	3,564	3,735
Owned Properties [Member] | Wichita, Kansas [Member]
Real Estate Properties [Line Items]
Buildings and improvements	1,409	1,409
Total Cost	1,409	1,409
Leased Properties [Member]
Real Estate Properties [Line Items]
Buildings and improvements	26,432	24,573
Construction in progress	628
Total Cost	27,060	24,573
Leased Properties [Member] | Jersey City, New Jersey [Member]
Real Estate Properties [Line Items]
Buildings and improvements	25,653	23,811
Construction in progress	628
Total Cost	26,281	23,811
Leased Properties [Member] | Overland Park, Kansas [Member]
Real Estate Properties [Line Items]
Buildings and improvements	779	762
Total Cost	$ 779	$ 762