Consolidated Statements Of Shareholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]
BALANCE at Dec. 31, 2017	$ 370,897,000	$ 815,000	$ 1,926,056,000	$ (1,555,974,000)
BALANCE, shares at Dec. 31, 2017		81,454,621
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,647,000		5,647,000
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	(6,000)	$ 6,000	(12,000)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		610,940
Dividends on preferred stock	(4,863,000)		(4,863,000)
Accretion on preferred stock	(753,000)		(753,000)
Loss on redemption of preferred stock	(7,133,000)		(7,133,000)
Net Income (loss)	27,492,000			27,492,000
BALANCE at Mar. 31, 2018	391,281,000	$ 821,000	1,918,942,000	(1,528,482,000)
BALANCE, shares at Mar. 31, 2018		82,065,561
BALANCE at Dec. 31, 2018	980,904,000	$ 916,000	2,131,535,000	(1,151,547,000)
BALANCE, shares at Dec. 31, 2018		91,627,738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	4,624,000		4,624,000
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	0	$ 9,000	(9,000)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		875,824
Dividends on preferred stock	(4,360,000)		(4,360,000)
Accretion on preferred stock	(801,000)		(801,000)
Loss on redemption of preferred stock	0
Net Income (loss)	151,363,000			151,363,000
BALANCE at Mar. 31, 2019	$ 1,131,730,000	$ 925,000	$ 2,130,989,000	$ (1,000,184,000)
BALANCE, shares at Mar. 31, 2019		92,503,562