Consolidated Statements Of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]
BALANCE at Dec. 31, 2017	$ 370,897	$ 815	$ 1,926,056	$ (1,555,974)
BALANCE, shares at Dec. 31, 2017		81,454,621
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Loss on redemption of preferred stock	(7,100)
BALANCE at Mar. 31, 2018	391,281	$ 821	1,918,942	(1,528,482)
BALANCE, shares at Mar. 31, 2018		82,065,561
BALANCE at Dec. 31, 2017	370,897	$ 815	1,926,056	(1,555,974)
BALANCE, shares at Dec. 31, 2017		81,454,621
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	10,757		10,757
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	(24)	$ 6	(30)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		652,923
Dividends on preferred stock	(9,337)		(9,337)
Accretion on preferred stock	(1,493)		(1,493)
Loss on redemption of preferred stock	(7,133)		(7,133)
Net Income (loss)	62,801			62,801
BALANCE at Jun. 30, 2018	426,468	$ 821	1,918,820	(1,493,173)
BALANCE, shares at Jun. 30, 2018		82,107,544
BALANCE at Mar. 31, 2018	391,281	$ 821	1,918,942	(1,528,482)
BALANCE, shares at Mar. 31, 2018		82,065,561
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,110		5,110
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	(18)	$ 0	(18)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		41,983
Dividends on preferred stock	(4,474)		(4,474)
Accretion on preferred stock	(740)		(740)
Loss on redemption of preferred stock	0
Net Income (loss)	35,309			35,309
BALANCE at Jun. 30, 2018	426,468	$ 821	1,918,820	(1,493,173)
BALANCE, shares at Jun. 30, 2018		82,107,544
BALANCE at Dec. 31, 2018	980,904	$ 916	2,131,535	(1,151,547)
BALANCE, shares at Dec. 31, 2018		91,627,738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	11,052		11,052
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	0	$ 10	(10)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		925,192
Dividends on preferred stock	(8,812)		(8,812)
Accretion on preferred stock	(1,634)		(1,634)
Loss on redemption of preferred stock	0
Net Income (loss)	258,848			258,848
BALANCE at Jun. 30, 2019	1,240,358	$ 926	2,132,131	(892,699)
BALANCE, shares at Jun. 30, 2019		92,552,930
BALANCE at Mar. 31, 2019	1,131,730	$ 925	2,130,989	(1,000,184)
BALANCE, shares at Mar. 31, 2019		92,503,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	6,428		6,428
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares	0	$ 1	(1)
Issuance of common stock upon grants of restricted stock awards and vestings of restricted stock units and performance shares, net of forfeitures, shares		49,368
Dividends on preferred stock	(4,452)		(4,452)
Accretion on preferred stock	(833)		(833)
Loss on redemption of preferred stock	0
Net Income (loss)	107,485			107,485
BALANCE at Jun. 30, 2019	$ 1,240,358	$ 926	$ 2,132,131	$ (892,699)
BALANCE, shares at Jun. 30, 2019		92,552,930