Supplemental Guarantor Financial Information - I/S (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		$ 1,093,999	$ 1,349,405	$ 1,345,243
Operating costs and expenses		1,036,067
Loss on disposal and impairment of assets		4,144	11,653	17,873
Income from operations		53,788	86,434	70,210
Interest expense (income), net, including amortization of deferred financing costs and note discount		49,258
Redemption costs for early extinguishment of debt	$ 3,000	3,018	0	6,408
Equity in earnings of subsidiaries		0
Other expense (income), net		(18,077)	(18,404)	(627)
Income before income taxes		19,589	64,787	14,113
Income tax (benefit) expense		452	16,522	10,457
Net income		19,137	48,265	3,656
Net loss attributable to noncontrolling interests		(7)	(9)	(20)
Net income attributable to controlling interests and available to common shareholders		19,144	48,274	3,676
Other comprehensive loss attributable to controlling interest		(15,924)
Comprehensive income (loss) attributable to controlling interests		3,220	$ 37,264	$ (29,609)
Eliminations
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		(70,791)
Operating costs and expenses		(71,662)
Loss on disposal and impairment of assets		0
Income from operations		871
Interest expense (income), net, including amortization of deferred financing costs and note discount		230
Redemption costs for early extinguishment of debt		0
Equity in earnings of subsidiaries		56,393
Other expense (income), net		(24,197)
Income before income taxes		(31,555)
Income tax (benefit) expense		0
Net income		(31,555)
Net loss attributable to noncontrolling interests		(7)
Net income attributable to controlling interests and available to common shareholders		(31,548)
Other comprehensive loss attributable to controlling interest		43,962
Comprehensive income (loss) attributable to controlling interests		12,414
Parent | Reportable Legal Entities
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		0
Operating costs and expenses		34,392
Loss on disposal and impairment of assets		0
Income from operations		(34,392)
Interest expense (income), net, including amortization of deferred financing costs and note discount		92
Redemption costs for early extinguishment of debt		0
Equity in earnings of subsidiaries		(50,900)
Other expense (income), net		4,730
Income before income taxes		11,686
Income tax (benefit) expense		(7,451)
Net income		19,137
Net loss attributable to noncontrolling interests		0
Net income attributable to controlling interests and available to common shareholders		19,137
Other comprehensive loss attributable to controlling interest		(15,924)
Comprehensive income (loss) attributable to controlling interests		3,213
Issuers | Reportable Legal Entities
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		614,090
Operating costs and expenses		596,398
Loss on disposal and impairment of assets		2,724
Income from operations		14,968
Interest expense (income), net, including amortization of deferred financing costs and note discount		44,205
Redemption costs for early extinguishment of debt		3,018
Equity in earnings of subsidiaries		(48,536)
Other expense (income), net		6,420
Income before income taxes		9,861
Income tax (benefit) expense		(2,606)
Net income		12,467
Net loss attributable to noncontrolling interests		0
Net income attributable to controlling interests and available to common shareholders		12,467
Other comprehensive loss attributable to controlling interest		(37,160)
Comprehensive income (loss) attributable to controlling interests		(24,693)
Guarantors | Reportable Legal Entities
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		281,752
Operating costs and expenses		204,770
Loss on disposal and impairment of assets		426
Income from operations		76,556
Interest expense (income), net, including amortization of deferred financing costs and note discount		5,978
Redemption costs for early extinguishment of debt		0
Equity in earnings of subsidiaries		43,625
Other expense (income), net		3,785
Income before income taxes		23,168
Income tax (benefit) expense		8,271
Net income		14,897
Net loss attributable to noncontrolling interests		0
Net income attributable to controlling interests and available to common shareholders		14,897
Other comprehensive loss attributable to controlling interest		(2,169)
Comprehensive income (loss) attributable to controlling interests		12,728
Non-Guarantors | Reportable Legal Entities
Condensed Consolidated Statements of Comprehensive (Loss) Income
Revenues		268,948
Operating costs and expenses		272,169
Loss on disposal and impairment of assets		994
Income from operations		(4,215)
Interest expense (income), net, including amortization of deferred financing costs and note discount		(1,247)
Redemption costs for early extinguishment of debt		0
Equity in earnings of subsidiaries		(582)
Other expense (income), net		(8,815)
Income before income taxes		6,429
Income tax (benefit) expense		2,238
Net income		4,191
Net loss attributable to noncontrolling interests		0
Net income attributable to controlling interests and available to common shareholders		4,191
Other comprehensive loss attributable to controlling interest		(4,633)
Comprehensive income (loss) attributable to controlling interests		$ (442)