Schedule III Real Estate and Accumulated Depreciation - Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Initial Cost
Land	$ 89,689
Building and Improvements	380,956
Costs Capitalized Subsequent to Acquisition	824,490
Gross Amount Carried As of Year End
Land	74,819
Building and Improvements	1,220,316
Total	1,295,135	$ 1,146,548	$ 1,048,525	$ 829,508
Accumulated Depreciation	284,219	$ 215,978	$ 155,704	$ 105,433
Aggregate cost of the total properties for federal income tax purposes	1,147,400
BO1 Somerville MA
Initial Cost
Land	6,100
Building and Improvements	26,748
Costs Capitalized Subsequent to Acquisition	64,882
Gross Amount Carried As of Year End
Land	5,154
Building and Improvements	92,576
Total	97,730
Accumulated Depreciation	36,496
CH1 Chicago IL
Initial Cost
Land	5,493
Building and Improvements	49,522
Costs Capitalized Subsequent to Acquisition	45,921
Gross Amount Carried As of Year End
Land	5,493
Building and Improvements	95,443
Total	100,936
Accumulated Depreciation	22,195
DC1 Washington DC
Initial Cost
Building and Improvements	4,797
Costs Capitalized Subsequent to Acquisition	3,462
Gross Amount Carried As of Year End
Building and Improvements	8,259
Total	8,259
Accumulated Depreciation	4,399
DE1 Denver CO
Initial Cost
Building and Improvements	37
Costs Capitalized Subsequent to Acquisition	3,308
Gross Amount Carried As of Year End
Building and Improvements	3,345
Total	3,345
Accumulated Depreciation	827
DE2 Denver CO
Initial Cost
Building and Improvements	4
Costs Capitalized Subsequent to Acquisition	1,068
Gross Amount Carried As of Year End
Building and Improvements	1,072
Total	1,072
Accumulated Depreciation	617
LA1 Los Angeles CA
Initial Cost
Building and Improvements	41,099
Costs Capitalized Subsequent to Acquisition	28,321
Gross Amount Carried As of Year End
Building and Improvements	69,420
Total	69,420
Accumulated Depreciation	26,029
LA2 Los Angeles CA
Initial Cost
Land	28,467
Building and Improvements	94,114
Costs Capitalized Subsequent to Acquisition	56,760
Gross Amount Carried As of Year End
Land	28,467
Building and Improvements	150,874
Total	179,341
Accumulated Depreciation	32,492
MI1 Miami FL
Initial Cost
Land	728
Building and Improvements	9,325
Costs Capitalized Subsequent to Acquisition	1,094
Gross Amount Carried As of Year End
Land	728
Building and Improvements	10,419
Total	11,147
Accumulated Depreciation	2,362
NY1 New York NY
Initial Cost
Costs Capitalized Subsequent to Acquisition	35,083
Gross Amount Carried As of Year End
Building and Improvements	35,083
Total	35,083
Accumulated Depreciation	16,677
NY2 Secaucus NJ
Initial Cost
Land	4,952
Building and Improvements	18,408
Costs Capitalized Subsequent to Acquisition	108,230
Gross Amount Carried As of Year End
Land	2,388
Building and Improvements	129,202
Total	131,590
Accumulated Depreciation	8,096
SV1 San Jose CA
Initial Cost
Land	6,863
Building and Improvements	91,719
Costs Capitalized Subsequent to Acquisition	37,686
Gross Amount Carried As of Year End
Land	6,863
Building and Improvements	129,405
Total	136,268
Accumulated Depreciation	23,462
SV2 Milpitas CA
Initial Cost
Land	5,086
Building and Improvements	5,046
Costs Capitalized Subsequent to Acquisition	22,504
Gross Amount Carried As of Year End
Land	5,086
Building and Improvements	27,550
Total	32,636
Accumulated Depreciation	14,883
SV3 Santa Clara CA
Initial Cost
Land	4,162
Building and Improvements	3,482
Costs Capitalized Subsequent to Acquisition	46,464
Gross Amount Carried As of Year End
Land	3,972
Building and Improvements	50,136
Total	54,108
Accumulated Depreciation	24,992
SV4 Santa Clara CA
Initial Cost
Land	4,632
Building and Improvements	3,716
Costs Capitalized Subsequent to Acquisition	90,182
Gross Amount Carried As of Year End
Land	4,501
Building and Improvements	94,029
Total	98,530
Accumulated Depreciation	22,683
SV5 Santa Clara CA
Initial Cost
Land	2,572
Costs Capitalized Subsequent to Acquisition	23,486
Gross Amount Carried As of Year End
Land	2,544
Building and Improvements	23,514
Total	26,058
Accumulated Depreciation	1,245
SV6 Santa Clara CA
Initial Cost
Land	4,741
Costs Capitalized Subsequent to Acquisition	25,500
Gross Amount Carried As of Year End
Building and Improvements	30,241
Total	30,241
SV7 Santa Clara CA
Initial Cost
Land	3,793
Costs Capitalized Subsequent to Acquisition	29,673
Gross Amount Carried As of Year End
Building and Improvements	33,466
Total	33,466
VA1 Reston VA
Initial Cost
Land	6,903
Building and Improvements	32,939
Costs Capitalized Subsequent to Acquisition	87,806
Gross Amount Carried As of Year End
Land	6,903
Building and Improvements	120,745
Total	127,648
Accumulated Depreciation	43,211
VA2 Reston VA
Initial Cost
Land	5,197
Costs Capitalized Subsequent to Acquisition	113,060
Gross Amount Carried As of Year End
Land	2,720
Building and Improvements	115,537
Total	118,257
Accumulated Depreciation	$ 3,553