Stockholder Rights Plan (Details)	Jan. 17, 2012 votes $ / shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2002 $ / shares shares
Temporary Equity [Line Items]
Original Rights Agreement, extended term	10 years
Ratio of preferred stock that can be purchased per right	0.001
Preferred stock, dividend rate (in dollars per share)	$ 1.00
Dividends, preferred stock, common share equivalents per share	1,000
Liquidation value per share (in dollars per share)	1,000
Preferred stock, liquidation preference per share of common stock	$ 1,000
Preferred stock, number of voting rights | votes	1,000
Distribution date	10 days
Common stock shares, market value as a percentage of purchase price	2
Minimum
Temporary Equity [Line Items]
Beneficial ownership, percentage	15.00%
Series A Preferred Stock
Temporary Equity [Line Items]
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00	$ 1.00	$ 1.00
Preferred stock, redemption price (in dollars per share)	$ 70,000
Preferred stock, shares authorized (in shares) | shares		16,000	16,000	16,000
Preferred stock, shares issued (in shares) | shares		0	0
Preferred stock, shares outstanding (in shares) | shares		0	0