Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Operating revenues	$ 477,464	$ 459,538	$ 921,349	$ 877,246
Cost of services (excluding depreciation and amortization shown below)	214,491	227,210	430,056	446,271
Selling, general and administrative expenses	124,061	122,798	238,467	251,022
Depreciation and amortization	46,701	47,106	93,544	96,325
Impairment loss	1,228	47,834	1,228	47,834
Total operating expenses	386,481	444,948	763,295	841,452
Operating income	90,983	14,590	158,054	35,794
Interest expense:
Interest income	98	401	512	1,379
Interest expense	17,743	19,582	35,936	39,285
Total interest expense, net	(17,645)	(19,181)	(35,424)	(37,906)
Gain/(loss) on investments and other, net	7,136	(2,884)	4,089	(2,150)
Tax indemnification release	0	(13,394)	0	(13,394)
Income/(loss) from continuing operations before equity in earnings/(losses) of affiliates and income taxes	80,474	(20,869)	126,719	(17,656)
Provision/(benefit) for income taxes	21,845	(15,031)	34,796	(13,973)
Income/(loss) from continuing operations before equity in earnings/(losses) of affiliates	58,629	(5,838)	91,923	(3,683)
Equity in earnings/(losses) of affiliates, net of tax	376	314	888	(108)
Net income/(loss) from continuing operations	59,005	(5,524)	92,811	(3,791)
(Loss)/income from discontinued operations, net of tax	0	(48)	13	(94)
Net income/(loss)	$ 59,005	$ (5,572)	$ 92,824	$ (3,885)
Basic income per share:
Net income from continuing operations (usd per share)	$ 0.74	$ (0.07)	$ 1.17	$ (0.05)
Loss from discontinued operations, net of tax (usd per share)	0	0	0	0
Net (loss)/income (usd per share)	0.74	(0.07)	1.17	(0.05)
Diluted income per share:
Net income from continuing operations (usd per share)	0.73	(0.07)	1.15	(0.05)
Loss from discontinued operations, net of tax (usd per share)	0	0	0	0
Net (loss)/income (usd per share)	$ 0.73	$ (0.07)	$ 1.15	$ (0.05)
Weighted-average common shares outstanding:
Basic (in shares)	79,403	80,473	79,216	80,326
Diluted (in shares)	80,646	80,473	80,767	80,326