Notes Receivable - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Note	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Note	Sep. 30, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2		2
Interest income	$ 2,982	$ 3,001	$ 9,383	$ 9,070
National Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2		2
Interest income	$ 3,000	$ 3,000	$ 9,300	9,100
Payment received relating to notes receivables			$ 9,400	$ 10,800