Schedule III - Real Estate Investments (Detail) (USD $) In Thousands, unless otherwise specified						12 Months Ended										12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 Owned Properties [Member]	Dec. 31, 2013 Owned Properties [Member] Suwanee, Georgia [Member]	Dec. 31, 2013 Owned Properties [Member] Atlanta, Georgia (Atlanta-Metro) [Member]	Dec. 31, 2013 Owned Properties [Member] Santa Clara, California [Member]	Dec. 31, 2013 Owned Properties [Member] Richmond, Virginia [Member]	Dec. 31, 2013 Owned Properties [Member] Sacramento, California [Member]	Dec. 31, 2013 Owned Properties [Member] Dallas, Texas [Member]	Dec. 31, 2013 Owned Properties [Member] Miami, Florida [Member]	Dec. 31, 2013 Owned Properties [Member] Lenexa, Kansas [Member]	Dec. 31, 2013 Owned Properties [Member] Wichita, Kansas [Member]	Dec. 31, 2013 Leased Properties [Member]	Dec. 31, 2013 Leased Properties [Member] Jersey City, New Jersey [Member]	Dec. 31, 2013 Leased Properties [Member] Overland Park, Kansas [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Initial costs of land	$ 19,700				$ 19,700	$ 1,395	$ 12,647		$ 2,000	$ 1,481		$ 1,777	$ 400
Initial costs of buildings and improvements	163,600				161,615	29,802	35,473	15,838	11,200	52,753	5,808	6,955	3,100	686	1,985	1,985
Costs capitalized subsequent to acquisition, Land	10,901				10,901	2,126	2,750		180		5,808		37
Costs capitalized subsequent to acquisition, Buildings and improvements	564,630				542,042	96,684	261,074	70,706	97,779	88	(5,808)	20,598	198	723	22,588	21,826	762
Costs capitalized subsequent to acquisition, Construction in progress	146,904				146,904	3,270	32,456	1,249	67,155	4,273	38,501
Gross carrying amount, Land	30,601				30,601	3,521	15,397		2,180	1,481	5,808	1,777	437
Gross carrying amount, Buildings and improvements	728,230				703,657	126,486	296,547	86,544	108,979	52,841		27,553	3,298	1,409	24,573	23,811	762
Gross carrying amount, Construction in progress	146,904				146,904	3,270	32,456	1,249	67,155	4,273	38,501
Accumulated depreciation and amortization	$ (137,725)	$ (102,900)	$ (74,536)	$ (52,923)	$ (128,605)	$ (34,590)	$ (58,272)	$ (19,102)	$ (8,996)	$ (1,403)		$ (5,662)	$ (82)	$ (498)	$ (9,120)	$ (8,686)	$ (434)
Date of acquisition						Sep. 01, 2005	Oct. 03, 2006	Nov. 01, 2007	Mar. 20, 2010	Dec. 21, 2012	Feb. 08, 2013	Mar. 06, 2008	Jun. 03, 2011	Mar. 31, 2005		Nov. 01, 2006