Notes Receivable - Loans Receivable on Real Estate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mortgage Loans on Real Estate [Line Items]
Balance at beginning of period	$ 84,541	$ 103,705	$ 58,719
New mortgage loans	10,239	10,000
Interest	876	811
Accretion of discount	826	780	250
Payments of principal	(104)	(25,755)	0
Loan loss reserve	(4,300)	(5,000)	0
Other	(31,700)	0
Balance at December 31	$ 60,378	$ 84,541	$ 103,705