Summary of Significant Accounting Policies and Practices - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Share-based compensation expense	$ 4,270	$ 3,704	$ 2,595
Maturity period of highly liquid investments	Three months or less
Percentage of subsidiaries owned	100.00%	100.00%	100.00%
Selling, General and Administrative Expense [Member]
Significant Accounting Policies [Line Items]
Share-based compensation expense	$ 4,300	$ 3,700	$ 2,600
Selling, General and Administrative Expense [Member] | Executive Officer [Member]
Significant Accounting Policies [Line Items]
Share-based compensation expense		$ 200	$ 200
Joint Venture [Member]
Significant Accounting Policies [Line Items]
Percentage of subsidiaries owned	49.00%
RFK [Member]
Significant Accounting Policies [Line Items]
Percentage of subsidiaries owned	99.70%