Real Estate and Lending Activities - Schedule of Revenue from External Customers by Geographic Areas (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 126,555	$ 114,570	$ 387,854	$ 310,333
Revenue [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 387,854	$ 310,333
Percentage of Total Revenue			100.00%	100.00%
Revenue [Member] | Texas [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 72,811	$ 63,815
Percentage of Total Revenue			18.80%	20.60%
Revenue [Member] | California [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 49,724	$ 49,595
Percentage of Total Revenue			12.80%	16.00%
Revenue [Member] | All Other States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 189,365	$ 137,006
Percentage of Total Revenue			48.80%	44.10%
Revenue [Member] | United States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 311,900	$ 250,416
Percentage of Total Revenue			80.40%	80.70%
Revenue [Member] | Germany [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 72,718	$ 56,609
Percentage of Total Revenue			18.80%	18.20%
Revenue [Member] | United Kingdom, Italy, and Spain [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 3,236	$ 3,308
Percentage of Total Revenue			0.80%	1.10%
Revenue [Member] | International [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue			$ 75,954	$ 59,917
Percentage of Total Revenue			19.60%	19.30%