Preferred Stock (Series E Redeemable Convertible Preferred Stock) (Narrative) (Details) - Series E Preferred Stock [Member] - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Feb. 28, 2018	Mar. 31, 2019	Dec. 31, 2018	Feb. 28, 2017
Class of Stock [Line Items]
Preferred stock, shares outstanding		925,000	925,000
Preferred stock, annual dividend rate		6.25%	6.25%
Preferred stock, dividend rate increase resulting from failure to pay dividend, with equity offerings		9.50%
Preferred stock, face value		$ 10.00
Redeemable preferred stock, liquidation preference per share		$ 10.00
Preferred stock, percentage of conversion price at which preferred stock automatically converts to common stock		120.00%
Preferred stock, trading days for preferred stock automatically converting to common stock		60 days
Number of shares redeemable by company when market price is within defined range		490,250
Preferred stock, percentage of liquidation value at which holders can sell		130.00%
Threshold of originally issued preferred stock shares outstanding required for approval of certain transactions by preferred shareholders		434,750
Threshold of originally issued preferred stock shares outstanding required for approval of certain transactions by preferred shareholders, percent		47.00%
Percentage of approval required for certain transactions by preferred shareholders		75.00%
Threshold of amount of related party transactions for approval by preferred shareholders		$ 120
Threshold of maximum percentage of shares grantable before shareholder approval required		9.90%
Preferred stock, value		$ 10,050	$ 10,050	$ 9,900
On Or After February 28,2019 [Member]
Class of Stock [Line Items]
Conversion price per share		$ 13.845
Minimum [Member]
Class of Stock [Line Items]
Preferred stock, percentage of liquidation value at which company can redeem preferred stock		110.00%
Maximum [Member]
Class of Stock [Line Items]
Preferred stock, percentage of liquidation value at which company can redeem preferred stock	130.00%
Level 3 [Member] | Redemption Rights [Member]
Class of Stock [Line Items]
Assets fair value				$ 150