Stockholders' Equity (Distribution of REIT Taxable Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Common and preferred dividends	$ 99,139	$ 1,077,179	$ 69,162
Dividends treated as taxable compensation	(130)	(92)	(94)
Portion of dividends declared in current year, and paid in current year, which was applied to the prior year distribution requirements	0	0	(731)
Portion of dividends declared in subsequent year, and paid in subsequent year, which apply to current year distribution requirements	0	0	0
Dividends in excess of current year REIT distribution requirements	0	(827,005)	0
Dividends applied to meet current year REIT distribution requirements	$ 99,009	$ 250,082	$ 68,337