Shareholders' Equity Rollforward (Details) - USD ($) $ in Thousands		3 Months Ended								9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019		Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		$ 590,539	$ 684,319	$ 520,745		$ 461,554	$ 408,944	$ 447,355		$ 520,745	$ 447,355
Net income (loss)		(243,413)	(94,715)	163,094		54,362	51,625	(38,697)		(175,034)	67,290
All Other Changes		606	935	556		742	985	380	[1]
As of ending balance		347,732	590,539	684,319		516,658	461,554	408,944		347,732	516,658
Share-based compensation		800				1,000				2,582	3,101
Accounting Standards Update 2016-13 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	[2]		(76)
As of ending balance	[2]			(76)
Accounting Standards Update 2016-02
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	[3]						(94)
As of ending balance	[3]							(94)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		(61)	(60)	(59)		80	81	82		(59)	82
All Other Changes		(2)	(1)	(1)			(1)	(1)
As of ending balance		(63)	(61)	(60)		80	80	81		(63)	80
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		388,290	483,005	319,987		262,326	210,701	249,492		319,987	249,492
Net income (loss)		(243,413)	(94,715)	163,094		54,362	51,625	(38,697)
All Other Changes				0				0
As of ending balance		144,877	388,290	483,005		316,688	262,326	210,701		144,877	316,688
Retained Earnings | Accounting Standards Update 2016-13 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	[2]		(76)
As of ending balance	[2]			(76)
Retained Earnings | Accounting Standards Update 2016-02
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	[3]						(94)
As of ending balance	[3]							(94)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		152	152	151		151	151	151		151	151
All Other Changes				1				0
As of ending balance		152	152	152		151	151	151		152	151
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		202,158	201,222	200,666		198,997	198,011	197,630		200,666	197,630
All Other Changes		608	936	556	[4]	742	986	381	[1]
As of ending balance		$ 202,766	$ 202,158	$ 201,222		$ 199,739	$ 198,997	$ 198,011		$ 202,766	$ 199,739

[1] Includes equity-classified share-based compensation of $3.1 million during the nine months ended September 30, 2019. During the nine months ended September 30, 2019, 42,534 shares of common stock were issued in connection with the vesting of certain RSUs, net of shares withheld for income taxes.

[2] to the adoption of ASU 2016–13 as of January 1, 2020 (see Note 4).

[3] 1     

[4] Includes equity-classified share-based compensation of $2.6 million during the nine months ended September 30, 2020. During the nine months ended September 30, 2020, 45,435 and 19,402 shares of common stock were issued in connection with the vesting of certain time-vested restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”), net of shares withheld for income taxes.