Acquisition of Real Estate - Purchase Price Allocation to Assets and Liabilities Acquired (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Business Acquisition Purchase Price Allocation [Line Items]
Land	$ 18,567
Site Improvements	13,342
Building Improvements	77,925
Tenant Improvements	1,526
Acquired In- Place Lease Value	12,640
Above Market Lease Value	3,200
Net Assets Acquired	127,200
2400 Dralle Road [Member]
Business Acquisition Purchase Price Allocation [Line Items]
Land	11,706
Site Improvements	4,732
Building Improvements	38,175
Tenant Improvements	912
Acquired In- Place Lease Value	6,645
Above Market Lease Value	2,080
Net Assets Acquired	64,250
Midwest Commerce Center I [Member]
Business Acquisition Purchase Price Allocation [Line Items]
Land	6,861	[1]
Site Improvements	8,610	[1]
Building Improvements	39,750	[1]
Tenant Improvements	614	[1]
Acquired In- Place Lease Value	5,995	[1]
Above Market Lease Value	1,120	[1]
Net Assets Acquired	$ 62,950	[1]

[1] Fair value determinations are preliminary. Final valuations of assets acquired are not yet complete.