Notes Receivable - Loans Receivable on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance at January 1	$ 41,988	$ 52,444
Additions:
New mortgage loans	11,139	0
Interest	377	0
Accretion of discount	1,038	980	$ 926
Deductions:
Collections of principal and interest	(5,054)	(11,436)
Balance at December 31	$ 49,488	$ 41,988	$ 52,444