Deferred Revenue-Entry of Right-to-Use Contracts and Deferred Commission Expense - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Deferred Revenue [Roll Forward]
Deferred revenue—upfront payments from right-to-use contracts, as of January 1,	$ 78,405	$ 74,174
Right-to-use contracts current period, gross	12,327	12,783	$ 13,892
Revenue recognized from right-to-use contract upfront payments	(9,248)	(8,552)	(8,391)
Right-to-use contract upfront payments, deferred, net	3,079	4,231
Deferred revenue—upfront payments from right-to-use contracts, as of December 31,	81,484	78,405	74,174
Movement in Deferred Costs [Roll Forward]
Deferred commission expense, as of January 1,	30,865	28,589
Deferred commission expense	4,659	5,871
Commission expense recognized	(4,149)	(3,595)	(2,934)
Net increase in deferred commission expense	510	2,276
Deferred commission expense, as of December 31,	$ 31,375	$ 30,865	$ 28,589