Notes Receivable - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) Note	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Note	Jun. 30, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 3,008	$ 3,393	$ 6,151	$ 6,401
National Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2		2
Interest income	$ 3,000	$ 3,400	$ 6,100	6,400
Payment received relating to notes receivables			$ 3,300	$ 3,400