Stockholders' Equity (Common and Preferred Stock) (Details)	3 Months Ended
	Mar. 31, 2019 Vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred shares authorized (in shares)	8,990,000
Preferred shares issued (in shares)	0
Convertible Series AA Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred shares authorized (in shares)	1,000,000
Annual cash dividend rate (in hundredths)	7.00%
Liquidation preference per share (in dollars per share) | $ / shares	$ 25.00
Initial conversion price (in dollars per share) | $ / shares	$ 25.00
Total number of common shares issuable upon conversion of outstanding shares of preferred stock (in shares)	2
Preferred shares issued (in shares)	0
Common Class A [Member]
Common Stock [Abstract]
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock shares issued (in shares)	17,733,947	17,721,422
Number of votes holder is entitled to | Vote	1
Maximum individual common stock ownership (in hundredths)	9.80%
Common Class B [Member]
Common Stock [Abstract]
Common stock, shares authorized (in shares)	1,000
Par value (in dollars per share) | $ / shares	$ 0.01
Common stock shares issued (in shares)	0
Number of votes holder is entitled to | Vote	1
Maximum individual common stock ownership (in hundredths)	9.80%