SCHEDULE III - REAL ESTATE ASSETS AND ACCUMULATED DEPRECIATION - Rollforward of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real estate:
Balance at the beginning of the year	$ 2,292,751	$ 2,277,457	$ 1,831,799
Acquisitions	4,145,977	150,782	482,125
Real estate acquired through loan receivable foreclosure	19,096	10,100	0
Addition due to consolidation of variable interest entity	0	0	10,700
Improvements	6,954	1,003	3,689
Impairment	(2,211)	(39,058)	0
Sale of real estate	(133,897)	(107,930)	(29,395)
Foreign currency translation	10,556	4,623	(16,944)
Write-off of fully depreciated assets	(4,371)	(4,226)	(4,517)
Balance at the end of the year	6,334,855	2,292,751	2,277,457
Accumulated depreciation:
Balance at the beginning of the year	(282,812)	(237,841)	(185,994)
Depreciation expense	(101,198)	(64,463)	(59,864)
Impairment	885	9,247	0
Sale of real estate	38,914	6,023	3,384
Foreign currency translation	(583)	(4)	116
Write-off of fully depreciated assets	4,371	4,226	4,517
Balance at the end of the year	$ (340,423)	$ (282,812)	$ (237,841)