Real Estate and Loans Receivable - Schedule of Revenue from External Customers by Geographic Areas (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue	$ 153,283	$ 126,555	$ 126,300	$ 134,999	$ 131,546	$ 114,570	$ 99,801	$ 95,961	$ 541,137	$ 441,878	$ 312,532
Revenue [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 541,137	$ 441,878
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									$ 96,992	$ 87,541
Percentage of Total Revenue									17.90%	19.80%
Revenue [Member] | California [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 66,197	$ 66,120
Percentage of Total Revenue									12.20%	15.00%
Revenue [Member] | New Jersey [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 39,084	$ 27,688
Percentage of Total Revenue									7.20%	6.30%
Revenue [Member] | Massachusetts [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 26,098	$ 69
Percentage of Total Revenue									4.80%	0.00%
Revenue [Member] | Arizona [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 23,798	$ 21,188
Percentage of Total Revenue									4.40%	4.80%
Revenue [Member] | Other States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 187,363	$ 156,256
Percentage of Total Revenue									34.70%	35.30%
Revenue [Member] | United States [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 439,532	$ 358,862
Percentage of Total Revenue									81.20%	81.20%
Revenue [Member] | Germany [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 97,382	$ 78,540
Percentage of Total Revenue									18.00%	17.80%
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									$ 4,223	$ 4,476
Percentage of Total Revenue									0.80%	1.00%
Revenue [Member] | International [Member] | Credit Concentration Risk [Member]
Investment And Revenue From External Customers By Geographic Area [Line Items]
Total Revenue									$ 101,605	$ 83,016
Percentage of Total Revenue									18.80%	18.80%