Stockholders' Equity (Narrative) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	9,940,000	9,940,000
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Common Stock [Member]
Class of Stock [Line Items]
Shares issued (in shares)	0	0	0