Related-Party Transactions - Additional Information (Detail) - 417 Oakbend, LP [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Related Party Transaction [Line Items]
Payments for rent	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Registration and legal fees expenses			$ 1.0
Chief Sales Officer [Member]
Related Party Transaction [Line Items]
General partnership ownership interest in related party, percentage	0.01%		0.01%
Limited partnership interest in related party, percentage	10.49%		10.49%