Segment Information - Segment Reconciliation of Operating Income to Net Income (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total Segment EBITDA	$ 96,753,000	$ 118,135,000	$ 201,686,000	$ 230,914,000
Interest expense	(19,170,000)	(18,012,000)	(34,842,000)	(37,942,000)
Depreciation and amortization	(29,908,000)	(37,606,000)	(49,626,000)	(75,429,000)
Other components of net periodic pension benefit (cost)	272,000	(936,000)	725,000	(1,137,000)
(Loss) on termination of leaseback obligations	(3,110,000)	0	(3,409,000)	0
Impairment charges	(3,611,000)	(18,132,000)	(3,611,000)	(18,230,000)
Restructuring and integration expenses	(3,489,000)	(7,347,000)	(12,723,000)	(17,192,000)
Transaction costs	(5,440,000)	(3,232,000)	(15,986,000)	(9,766,000)
Stock-based compensation expense (benefit)	(1,921,000)	(580,000)	(3,892,000)	5,484,000
Gain (loss) from remeasurement of indemnification asset	844,000	(617,000)	844,000	(4,418,000)
Other	1,251,000	955,000	1,620,000	1,855,000
Income before (provision) for income taxes	32,471,000	32,628,000	80,786,000	74,139,000
Severance costs	566,000	4,005,000	1,170,000	7,349,000
COVID-19 Terminations
Segment Reporting Information [Line Items]
Severance costs	$ 0	$ 4,000,000.0	$ 0	$ 5,000,000.0