Real Estate Assets and Construction in Progress - Summary of Properties Owned or Leased by the Company (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Real Estate Properties [Line Items]
Land	$ 30,601	$ 24,713
Buildings and improvements	728,230	622,506
Construction in progress	146,904	87,609
Total Cost	905,735	734,828
Owned Properties [Member]
Real Estate Properties [Line Items]
Land	30,601	24,713
Buildings and improvements	703,657	603,121
Construction in progress	146,904	85,721
Total Cost	881,162	713,555
Owned Properties [Member] | Suwanee, Georgia (Atlanta-Suwanee) [Member]
Real Estate Properties [Line Items]
Land	3,521	3,521
Buildings and improvements	126,486	103,438
Construction in progress	3,270	3,572
Total Cost	133,277	110,531
Owned Properties [Member] | Atlanta, Georgia (Atlanta-Metro) [Member]
Real Estate Properties [Line Items]
Land	15,397
Buildings and improvements	296,547
Construction in progress	32,456
Total Cost	344,400
Owned Properties [Member] | Santa Clara, California [Member]
Real Estate Properties [Line Items]
Buildings and improvements	86,544	83,536
Construction in progress	1,249	245
Total Cost	87,793	83,781
Owned Properties [Member] | Richmond, Virginia [Member]
Real Estate Properties [Line Items]
Land	2,180	2,179
Buildings and improvements	108,979	71,629
Construction in progress	67,155	71,986
Total Cost	178,314	145,794
Owned Properties [Member] | Sacramento, California [Member]
Real Estate Properties [Line Items]
Land	1,481	1,485
Buildings and improvements	52,841	52,753
Construction in progress	4,273
Total Cost	58,595	54,238
Owned Properties [Member] | Dallas, Texas [Member]
Real Estate Properties [Line Items]
Land	5,808
Construction in progress	38,501
Total Cost	44,309
Owned Properties [Member] | Miami, Florida [Member]
Real Estate Properties [Line Items]
Land	1,777	1,777
Buildings and improvements	27,553	27,111
Total Cost	29,330	28,888
Owned Properties [Member] | Lenexa, Kansas [Member]
Real Estate Properties [Line Items]
Land	437	437
Buildings and improvements	3,298	54
Construction in progress		3,260
Total Cost	3,735	3,751
Owned Properties [Member] | Wichita, Kansas [Member]
Real Estate Properties [Line Items]
Buildings and improvements	1,409	1,408
Total Cost	1,409	1,408
Owned Properties [Member] | Atlanta, Georgia (Atlanta-Metro) [Member]
Real Estate Properties [Line Items]
Land		15,314
Buildings and improvements		263,192
Construction in progress		6,658
Total Cost		285,164
Leased Properties [Member]
Real Estate Properties [Line Items]
Buildings and improvements	24,573	19,385
Construction in progress		1,888
Total Cost	24,573	21,273
Leased Properties [Member] | Jersey City, New Jersey [Member]
Real Estate Properties [Line Items]
Buildings and improvements	23,811	18,666
Construction in progress		1,888
Total Cost	23,811	20,554
Leased Properties [Member] | Overland Park, Kansas [Member]
Real Estate Properties [Line Items]
Buildings and improvements	762	719
Total Cost	$ 762	$ 719