Stockholders' Equity - Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015	Dec. 31, 2014
Minimum
Dividends
Common stock distributions as percentage of REIT taxable income		90.00%
Common stock distributions as percentage of net income (after tax), from foreclosure property		90.00%
Common Stock
Dividends
Ordinary income (in dollars per share)		$ 2.36	$ 1.70				$ 1.15
Total dividend (in dollars per share)		2.36	1.70				1.15
Dividend declared taxable	$ 0.44	0.41	0.32
Ordinary dividend paid (in dollars per share)				$ 0.80	$ 0.53	$ 0.42
Preferred Stock
Dividends
Ordinary income (in dollars per share)		1.81	1.81				1.81
Total dividend (in dollars per share)		$ 1.81	$ 1.81				$ 1.81
Ordinary dividend paid (in dollars per share)				$ 0.45	$ 0.45	$ 0.45