Stockholders' Equity (Tax Status of Distributions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock
Class of Stock [Line Items]
Tax Status of Common Stock Dividends Per Share Declared (in usd per share)	$ 2.853075	$ 0.320000	$ 0.300000
Nondividend Distribution Per Share (in usd per share)	2.190636	0.000000	0.000000
Series B Preferred Stock
Class of Stock [Line Items]
Tax Status of Preferred Stock Dividends Per Share Declared (in usd per share)			25.776040
Nondividend Distribution Per Share (in usd per share)			0.000000
Ordinary Dividends | Common Stock
Class of Stock [Line Items]
Tax Status of Common Stock Dividends Per Share Declared (in usd per share)	0.079661	0.161738	0.281564
Ordinary Dividends | Series B Preferred Stock
Class of Stock [Line Items]
Tax Status of Preferred Stock Dividends Per Share Declared (in usd per share)			0.467750
Long-Term Capital Gain | Common Stock
Class of Stock [Line Items]
Tax Status of Common Stock Dividends Per Share Declared (in usd per share)	0.582778	0.158262	0.018436
Unrecaptured Section 1250 Gain (in usd per share)	0.100934	0.097271	0.018436
Cash Liquidation Distributions (in usd per share)	$ 0.000000	$ 0.000000	0.000000
Long-Term Capital Gain | Series B Preferred Stock
Class of Stock [Line Items]
Tax Status of Preferred Stock Dividends Per Share Declared (in usd per share)			0.001000
Unrecaptured Section 1250 Gain (in usd per share)			0.001000
Cash Liquidation Distributions (in usd per share)			$ 25.307290