Significant Tenant - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Real Estate Properties [Line Items]
Rental revenues	$ 56,778	$ 57,880
Customer Concentration Risk | Sales Revenue Services Net
Real Estate Properties [Line Items]
Percentage of minimum revenue threshold contributed by one tenant	10.00%
Bloomberg | Customer Concentration Risk | Sales Revenue Services Net
Real Estate Properties [Line Items]
Percentage rent contributed by tenant	48.00%	45.00%
Real Estate | Bloomberg | Customer Concentration Risk | Sales Revenue Services Net
Real Estate Properties [Line Items]
Rental revenues	$ 27,004	$ 26,324