Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Operating revenues	$ 458,957	$ 451,768	$ 1,336,203	$ 1,385,069
Cost of services (excluding depreciation and amortization shown below)	228,186	230,419	674,457	709,154
Selling, general and administrative expenses	111,276	113,075	362,298	340,049
Depreciation and amortization	45,717	48,461	142,042	141,948
Impairment loss	78	33	47,912	82
Total operating expenses	385,257	391,988	1,226,709	1,191,233
Operating income	73,700	59,780	109,494	193,836
Interest expense:
Interest income	349	299	1,728	1,053
Interest expense	19,852	19,382	59,137	56,061
Total interest expense, net	(19,503)	(19,083)	(57,409)	(55,008)
Gain/(loss) on investments and other, net	224	2,835	(1,926)	5,124
Tax indemnification release	0	0	(13,394)	0
Income from continuing operations before equity in earnings/(losses) of affiliates and income taxes	54,421	43,532	36,765	143,952
Provision for income taxes	14,481	20,836	508	37,432
Income from continuing operations before equity in earnings/(losses) of affiliates	39,940	22,696	36,257	106,520
Equity in earnings/(losses) of affiliates, net of tax	605	(161)	497	2,909
Net income from continuing operations	40,545	22,535	36,754	109,429
Loss from discontinued operations, net of tax	(17,362)	(84)	(17,456)	(175)
Net income	$ 23,183	$ 22,451	$ 19,298	$ 109,254
Basic income per share:
Net income from continuing operations (usd per share)	$ 0.51	$ 0.28	$ 0.46	$ 1.35
Loss from discontinued operations, net of tax (usd per share)	(0.22)	0	(0.22)	0
Net (loss)/income (usd per share)	0.29	0.28	0.24	1.35
Diluted income per share:
Net income from continuing operations (usd per share)	0.50	0.27	0.45	1.33
Loss from discontinued operations, net of tax (usd per share)	(0.21)	0	(0.21)	0
Net (loss)/income (usd per share)	$ 0.29	$ 0.27	$ 0.24	$ 1.33
Weighted-average common shares outstanding:
Basic (in shares)	79,761	80,680	80,138	81,073
Diluted (in shares)	80,914	82,017	81,205	82,528