Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Impact of adoption	Preferred Stock	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings / (Accumulated Deficit)	Retained Earnings / (Accumulated Deficit) Impact of adoption
Balance (in shares) at Dec. 31, 2018			0	48,103,000
Balance at Dec. 31, 2018	$ 277,589	$ 37	$ 0	$ 481	$ 341,139		$ (64,031)	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				147,000
Common stock issued in connection with equity-based plans	1,591			$ 1	1,590
Vesting of common stock subject to repurchase	2				2
Stock-based compensation expense	4,267				4,267
Net income / (loss) attributable to common stockholders	9,010						9,010
Balance (in shares) at Mar. 31, 2019			0	48,250,000
Balance at Mar. 31, 2019	292,496		$ 0	$ 482	346,998		(54,984)
Balance (in shares) at Dec. 31, 2018			0	48,103,000
Balance at Dec. 31, 2018	$ 277,589	37	$ 0	$ 481	341,139		(64,031)	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchases of treasury stock (in shares)	0
Net income / (loss) attributable to common stockholders	$ 40,496
Balance (in shares) at Sep. 30, 2019			0	48,572,000
Balance at Sep. 30, 2019	336,166		$ 0	$ 486	359,178		(23,498)
Ending balance at Dec. 31, 2019	11,210
Balance (in shares) at Dec. 31, 2018			0	48,103,000
Balance at Dec. 31, 2018	277,589	37	$ 0	$ 481	341,139		(64,031)	37
Balance (in shares) at Dec. 31, 2019			0	48,701,000		0
Balance at Dec. 31, 2019	$ 355,651	(816)	$ 0	$ 487	365,627	$ 0	(10,463)	(816)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Balance (in shares) at Mar. 31, 2019			0	48,250,000
Balance at Mar. 31, 2019	$ 292,496		$ 0	$ 482	346,998		(54,984)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				232,000
Common stock issued in connection with equity-based plans	701			$ 3	698
Vesting of common stock subject to repurchase	2				2
Stock-based compensation expense	5,433				5,433
Net income / (loss) attributable to common stockholders	13,796						13,796
Balance (in shares) at Jun. 30, 2019			0	48,482,000
Balance at Jun. 30, 2019	312,428		$ 0	$ 485	353,131		(41,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				90,000
Common stock issued in connection with equity-based plans	1,012			$ 1	1,011
Vesting of common stock subject to repurchase	$ 2				2
Purchases of treasury stock (in shares)	0
Stock-based compensation expense	$ 5,034				5,034
Net income / (loss) attributable to common stockholders	17,690						17,690
Balance (in shares) at Sep. 30, 2019			0	48,572,000
Balance at Sep. 30, 2019	336,166		$ 0	$ 486	359,178		(23,498)
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income / (loss) attributable to common stockholders	(236)
Ending balance at Mar. 31, 2020	10,974
Balance (in shares) at Dec. 31, 2019			0	48,701,000		0
Balance at Dec. 31, 2019	355,651	(816)	$ 0	$ 487	365,627	$ 0	(10,463)	(816)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				107,000
Common stock issued in connection with equity-based plans	$ 1,365			$ 1	1,364
Purchases of treasury stock (in shares)	147,153					147,000
Purchases of treasury stock	$ (5,149)					$ (5,149)
Stock-based compensation expense	6,358				6,358
Net income / (loss) attributable to common stockholders	8,807						8,807
Balance (in shares) at Mar. 31, 2020			0	48,808,000		147,000
Balance at Mar. 31, 2020	366,216		$ 0	$ 488	373,349	$ (5,149)	(2,472)
Beginning balance at Dec. 31, 2019	11,210
Ending balance at Sep. 30, 2020	10,711
Balance (in shares) at Dec. 31, 2019			0	48,701,000		0
Balance at Dec. 31, 2019	355,651	$ (816)	$ 0	$ 487	365,627	$ 0	(10,463)	$ (816)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income / (loss) attributable to common stockholders	61,886
Balance (in shares) at Sep. 30, 2020			0	49,256,000		147,000
Balance at Sep. 30, 2020	$ 438,716		$ 0	$ 493	392,765	$ (5,149)	50,607
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance at Mar. 31, 2020	$ 10,974
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion adjustments of redeemable noncontrolling interest to redemption value	112
Net income / (loss) attributable to common stockholders	(370)
Ending balance at Jun. 30, 2020	10,716
Balance (in shares) at Mar. 31, 2020			0	48,808,000		147,000
Balance at Mar. 31, 2020	366,216		$ 0	$ 488	373,349	$ (5,149)	(2,472)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				263,000
Common stock issued in connection with equity-based plans	3,059			$ 3	3,056
Stock-based compensation expense	7,095				7,095
Accretion adjustments of redeemable noncontrolling interest to redemption value	(112)				(112)
Net income / (loss) attributable to common stockholders	16,995						16,995
Balance (in shares) at Jun. 30, 2020			0	49,071,000		147,000
Balance at Jun. 30, 2020	393,253		$ 0	$ 491	383,388	$ (5,149)	14,523
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion adjustments of redeemable noncontrolling interest to redemption value	254
Net income / (loss) attributable to common stockholders	(259)
Ending balance at Sep. 30, 2020	10,711
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in connection with equity-based plans (in shares)				185,000
Common stock issued in connection with equity-based plans	$ 2,185			$ 2	2,183
Purchases of treasury stock (in shares)	0
Stock-based compensation expense	$ 7,448				7,448
Accretion adjustments of redeemable noncontrolling interest to redemption value	(254)				(254)
Net income / (loss) attributable to common stockholders	36,084						36,084
Balance (in shares) at Sep. 30, 2020			0	49,256,000		147,000
Balance at Sep. 30, 2020	$ 438,716		$ 0	$ 493	$ 392,765	$ (5,149)	$ 50,607