Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020	[1]	Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019	[2]	Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019	[3]	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 100,617		$ 95,481		$ 81,923		$ 159,692		$ 159,080		$ 159,979		$ 157,480		$ 156,527		$ 437,714		$ 633,066		$ 606,299
Gross margin	44,168		45,382		45,879		42,713		47,271		46,852		44,903		42,303
Income before income taxes	15,793		23,236		23,959		11,411		23,417		22,864		15,743		3,486		74,399		65,510		124,948
Income from continuing operations	14,642		16,750		17,202		8,275		17,853		16,688		10,837		(161)		56,869		45,217		97,902
Income (loss) from discontinued operations, net of income tax	(26,260)		(59,168)		11,309		(206,381)		(340,943)		(2,769)		7,299		4,375		(280,500)		(332,038)		901
Net income (loss)	$ (11,618)		$ (42,418)		$ 28,511		$ (198,106)		$ (323,090)		$ 13,919		$ 18,136		$ 4,214		$ (223,631)		$ (286,821)		$ 98,803
Earnings (loss) per share - basic:
Continuing operations	$ 0.30	[4]	$ 0.34	[4]	$ 0.35	[4]	$ 0.17	[4]	$ 0.37	[4]	$ 0.35	[4]	$ 0.23	[4]			$ 1.17		$ 0.97		$ 2.44
Discontinued operations	(0.54)	[4]	(1.21)	[4]	0.23	[4]	(4.25)	[4]	(7.06)	[4]	(0.06)	[4]	0.15	[4]	$ 0.10	[4]	(5.75)		(7.14)		0.02
Net income (loss)	(0.24)	[4]	(0.87)	[4]	0.59	[4]	(4.08)	[4]	(6.69)	[4]	0.29	[4]	0.38	[4]	0.10	[4]	(4.59)	[5]	(6.17)	[5]	2.47	[5]
Earnings (loss) per share – diluted:
Continuing operations	0.29	[4]	0.34	[4]	0.35	[4]	0.17	[4]	0.37	[4]	0.34	[4]	0.22	[4]			1.16		0.96		2.27
Discontinued operations	(0.53)	[4]	(1.20)	[4]	0.23	[4]	(4.22)	[4]	(6.97)	[4]	(0.06)	[4]	0.15	[4]	0.10	[4]	(5.70)		(7.05)		0.02
Net income (loss)	$ (0.23)	[4]	$ (0.86)	[4]	$ 0.58	[4]	$ (4.05)	[4]	$ (6.61)	[4]	$ 0.29	[4]	$ 0.37	[4]	$ 0.10	[4]	$ (4.54)		$ (6.09)		$ 2.29

[1] Income from continuing operations for the fourth quarter of 2020 includes strategic project costs, CEO transition costs, and acquisition and integration costs of $2.3 million, $1.0 million, and $0.6 million, respectively, each of which were primarily recorded to selling, general, and administrative expenses.

[2] Income from continuing operations for the fourth quarter of 2019 includes acquisition, integration, and project costs totaling $4.3 million, which were primarily recorded to selling, general, and administrative expenses.

[3] The impact of potentially dilutive securities for the three months ended March 31, 2019 was not considered because the impact on continuing operations would be anti-dilutive.

[4] We calculated earnings per share for each of the quarters based on the weighted average number of shares and dilutive securities outstanding for each period. Accordingly, the sum of the quarters may not necessarily be equal to the full year income per share.

[5] Figures may not add due to rounding.