Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at at Dec. 31, 2015	$ 364,157	$ 641	$ 518,259	$ (55,731)	$ (99,012)
Balance at (in shares) at Dec. 31, 2015		64,077,140
Stock-based compensation plans
Grant of restricted stock	0	$ 2	(2)
Grant of restricted stock (in shares)		171,500
Issuance of common shares, net of withholdings	(2,300)	$ 0	(2,300)
Withholdings of common shares, net of issuances (in shares)		42,796
Forfeited restricted stock	0	$ 0	0
Stock Repurchased and Retired During Period, Shares		(4,825,545)
Stock Repurchased and Retired During Period, Value	(63,570)	$ (48)	(63,522)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	1,087		1,087
Adjustments to Additional Paid in Capital, Warrant Issued	(13,271)		13,271
Forfeited restricted stock (in shares)		(4,600)
Amortization of stock awards and restricted stock	3,165		3,165
Total comprehensive income (loss)	42,634			23,488	19,146
Balance at at Dec. 31, 2016	331,902	$ 595	443,416	(32,243)	(79,866)
Balance at (in shares) at Dec. 31, 2016		59,461,291
Stock-based compensation plans
Grant of restricted stock	0	$ 1	(1)
Grant of restricted stock (in shares)		113,000
Issuance of common shares, net of withholdings	(2,914)	$ 0	(2,914)
Issuance of common shares, net of withholdings (in shares)		17,441
Forfeited restricted stock	0	$ 0	0
Stock Repurchased and Retired During Period, Shares		(530,637)
Stock Repurchased and Retired During Period, Value	(11,184)	$ (5)	(11,179)
Adjustments to Additional Paid in Capital, Warrant Issued	38,502		(38,502)
Forfeited restricted stock (in shares)		(3,900)
Amortization of stock awards and restricted stock	3,632		3,632
Total comprehensive income (loss)	35,341			18,495	16,846
Balance at at Dec. 31, 2017	$ 395,279	$ 591	471,456	(13,748)	(63,020)
Balance at (in shares) at Dec. 31, 2017	59,057,195	59,057,195
Stock-based compensation plans
Grant of restricted stock	$ 0	$ 2	(2)
Grant of restricted stock (in shares)		198,900
Issuance of common shares, net of withholdings	(2,329)	$ 0	(2,329)
Withholdings of common shares, net of issuances (in shares)		36,378
Forfeited restricted stock	0	$ 0	0
Stock Repurchased and Retired During Period, Shares		(157,000)
Stock Repurchased and Retired During Period, Value	(3,580)	$ (2)	(3,578)
Bond hedge reclassification	(50,435)		(50,435)
Note conversion obligation reclassification	50,999		50,999
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | Accounting Standards Update 2014-09 [Member]	514			514
Forfeited restricted stock (in shares)		(1,300)
Amortization of stock awards and restricted stock	5,047		5,047
Total comprehensive income (loss)	40,943			69,285	(28,342)
Balance at at Dec. 31, 2018	$ 436,438	$ 591	$ 471,158	$ 56,051	$ (91,362)
Balance at (in shares) at Dec. 31, 2018	59,134,173	59,134,173