Notes Receivable - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Note	Jun. 30, 2013	Jun. 30, 2014 Note	Jun. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable	2		2
Interest income	$ 3,038,000	$ 3,052,000	$ 6,069,000	$ 6,103,000
National Bonds [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of notes receivable	2		2
Interest income	3,000,000	3,100,000	6,100,000	6,100,000
Payment received relating to notes receivables			$ 3,500,000	$ 3,500,000