Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Revenue	$ 280,650	$ 297,290	$ 923,020	$ 868,943
Cost of services	105,011	104,167	321,543	314,934
Gross profit	175,639	193,123	601,477	554,009
Operating expenses:
Sales and marketing	89,891	94,343	275,659	258,277
General and administrative	54,670	32,983	159,514	107,362
Impairment charges	0	0	222	3,611
Total operating expenses	144,561	127,326	435,395	369,250
Operating income	31,078	65,797	166,082	184,759
Other income (expense):
Interest expense	(13,720)	(12,050)	(40,584)	(38,159)
Interest expense, related party	(850)	(4,496)	(3,505)	(13,229)
Other components of net periodic pension (cost) benefit	(3,928)	273	5,295	998
Other income (expense)	6,941	(98)	15,567	(4,157)
Income before income tax expense	19,521	49,426	142,855	130,212
Income tax expense	(6,241)	(13,802)	(38,062)	(33,723)
Net income	13,280	35,624	104,793	96,489
Other comprehensive income (loss):
Foreign currency translation adjustment	(7,920)	(4,100)	(12,611)	(8,545)
Comprehensive income	$ 5,360	$ 31,524	$ 92,182	$ 87,944
Net income per common share:
Basic (in dollars per share)	$ 0.39	$ 1.05	$ 3.06	$ 2.87
Diluted (in dollars per share)	$ 0.37	$ 0.95	$ 2.86	$ 2.67
Weighted-average shares used in computing basic and diluted net income per common share:
Basic (in shares)	34,269,274	34,013,897	34,289,333	33,585,488
Diluted (in shares)	35,811,473	37,620,116	36,698,395	36,110,702