Real Estate and Lending Activities - Schedule of Revenue from External Customers by Geographic Areas (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 134,999	$ 95,961
Revenue [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 134,999	$ 95,961
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	$ 24,472	$ 21,016
Percentage of Total Revenue	18.10%	21.90%
Revenue [Member] | California [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 16,597	$ 16,539
Percentage of Total Revenue	12.30%	17.20%
Revenue [Member] | All Other States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 69,315	$ 42,114
Percentage of Total Revenue	51.40%	43.90%
Revenue [Member] | United States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 110,384	$ 79,669
Percentage of Total Revenue	81.80%	83.00%
Revenue [Member] | Germany [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 23,510	$ 15,210
Percentage of Total Revenue	17.40%	15.90%
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	$ 1,105	$ 1,082
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	$ 24,615	$ 16,292
Percentage of Total Revenue	18.20%	17.00%