CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings
Balance at beginning of period (in shares) at Dec. 31, 2019		100,624
Balance at beginning of period at Dec. 31, 2019	$ 969,305	$ 101	$ 826,629	$ 142,575
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	471		471
Issuance of equity awards, net (in shares)		154
Tax withholdings paid for net settlement of equity awards	(456)		(456)
Net loss	(7,804)			(7,804)
Balance at end of period (in shares) at Mar. 31, 2020		100,778
Balance at end of period at Mar. 31, 2020	961,516	$ 101	826,644	134,771
Balance at beginning of period (in shares) at Dec. 31, 2019		100,624
Balance at beginning of period at Dec. 31, 2019	969,305	$ 101	826,629	142,575
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(62,908)
Balance at end of period (in shares) at Sep. 30, 2020		100,898
Balance at end of period at Sep. 30, 2020	911,767	$ 101	831,999	79,667
Balance at beginning of period (in shares) at Mar. 31, 2020		100,778
Balance at beginning of period at Mar. 31, 2020	961,516	$ 101	826,644	134,771
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	2,962		2,962
Issuance of equity awards, net (in shares)		111
Tax withholdings paid for net settlement of equity awards	(129)		(129)
Net loss	(25,920)			(25,920)
Balance at end of period (in shares) at Jun. 30, 2020		100,889
Balance at end of period at Jun. 30, 2020	938,429	$ 101	829,477	108,851
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	2,535		2,535
Issuance of equity awards, net (in shares)		9
Tax withholdings paid for net settlement of equity awards	(13)		(13)
Net loss	(29,184)			(29,184)
Balance at end of period (in shares) at Sep. 30, 2020		100,898
Balance at end of period at Sep. 30, 2020	911,767	$ 101	831,999	79,667
Balance at beginning of period (in shares) at Dec. 31, 2020		100,913
Balance at beginning of period at Dec. 31, 2020	870,771	$ 101	835,115	35,555
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	2,487		2,487
Issuance of equity awards, net (in shares)		1,145
Issuance of equity awards, net	0	$ 1	(1)
Tax withholdings paid for net settlement of equity awards	(5,614)		(5,614)
Net loss	(20,375)			(20,375)
Balance at end of period (in shares) at Mar. 31, 2021		102,058
Balance at end of period at Mar. 31, 2021	847,269	$ 102	831,987	15,180
Balance at beginning of period (in shares) at Dec. 31, 2020		100,913
Balance at beginning of period at Dec. 31, 2020	870,771	$ 101	835,115	35,555
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(33,953)
Balance at end of period (in shares) at Sep. 30, 2021		103,260
Balance at end of period at Sep. 30, 2021	842,815	$ 103	841,110	1,602
Balance at beginning of period (in shares) at Mar. 31, 2021		102,058
Balance at beginning of period at Mar. 31, 2021	847,269	$ 102	831,987	15,180
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	2,909		2,909
Issuance of equity awards, net (in shares)		1,169
Issuance of equity awards, net	0	$ 1	(1)
Tax withholdings paid for net settlement of equity awards	(159)		(159)
Proceeds from exercise of stock awards	3,235		3,235
Net loss	(8,511)			(8,511)
Balance at end of period (in shares) at Jun. 30, 2021		103,227
Balance at end of period at Jun. 30, 2021	844,743	$ 103	837,971	6,669
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation cost	3,009		3,009
Issuance of equity awards, net (in shares)		33
Proceeds from exercise of stock awards	130		130
Net loss	(5,067)			(5,067)
Balance at end of period (in shares) at Sep. 30, 2021		103,260
Balance at end of period at Sep. 30, 2021	$ 842,815	$ 103	$ 841,110	$ 1,602