Notes Receivable - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) Note	Mar. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 2,948	$ 3,143
National Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2
Interest income	$ 2,900	3,100
Payment received relating to notes receivables	$ 3,200	$ 3,300