Schedule III - Activity of Real Estate Assets and Accumulated Depreciation Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Real estate assets, beginning balance	$ 1,604,648	$ 1,048,142	$ 643,974
Acquisitions through foreclosure	40,436	206,987	470,221
Other acquisitions	525,983	778,173	118,297
Improvements	40,312	50,182	25,802
Cost of real estate sold	(337,519)	(478,836)	(210,152)
Real estate assets, ending balance		1,604,648	1,048,142
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Accumulated depreciation, beginning balance	62,601	61,716	19,367
Depreciation expense	48,989	20,840	6,414
Selling cost and impairment	38,764	56,384	70,124
Losses resulting from natural disasters	3,564	0	0
Real estate sold	(49,329)	(76,339)	(34,189)
Accumulated depreciation, ending balance	104,589	$ 62,601	$ 61,716
Aggregate cost for federal income tax purposes	$ 1,544,800