Notes Receivable - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) Note	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Note	Jun. 30, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2		2
Interest income	$ 3,393	$ 3,038	$ 6,401	$ 6,069
National Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable | Note	2		2
Interest income	$ 3,400	$ 3,000	$ 6,400	6,100
Payment received relating to notes receivables			$ 3,400	$ 3,500