Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Operating revenues	$ 459,538	$ 488,401	$ 877,246	$ 933,301
Cost of services (excluding depreciation and amortization shown below)	227,210	239,346	446,271	478,735
Selling, general and administrative expenses	122,798	112,022	251,022	226,974
Depreciation and amortization	47,106	47,347	96,325	93,487
Impairment loss	47,834	49	47,834	49
Total operating expenses	444,948	398,764	841,452	799,245
Operating income	14,590	89,637	35,794	134,056
Interest expense:
Interest income	401	224	1,379	754
Interest expense	19,582	18,987	39,285	36,679
Total interest expense, net	(19,181)	(18,763)	(37,906)	(35,925)
(Loss)/gain on investments and other, net	(2,884)	2,128	(2,150)	2,289
Tax indemnification release	(13,394)	0	(13,394)	0
(Loss)/income from continuing operations before equity in earnings/(losses) of affiliates and income taxes	(20,869)	73,002	(17,656)	100,420
(Benefit)/provision for income taxes	(15,031)	17,307	(13,973)	16,596
(Loss)/income from continuing operations before equity in earnings/(losses) of affiliates	(5,838)	55,695	(3,683)	83,824
Equity in earnings/(losses) of affiliates, net of tax	314	2,837	(108)	3,070
Net (loss)/income from continuing operations	(5,524)	58,532	(3,791)	86,894
Loss from discontinued operations, net of tax	(48)	(16)	(94)	(91)
Net (loss)/income	$ (5,572)	$ 58,516	$ (3,885)	$ 86,803
Basic (loss)/income per share:
Net (loss)/income from continuing operations (usd per share)	$ (0.07)	$ 0.72	$ (0.05)	$ 1.07
Loss from discontinued operations, net of tax (usd per share)	0	0	0	0
Net (loss)/income (usd per share)	(0.07)	0.72	(0.05)	1.07
Diluted (loss)/income per share:
Net income from continuing operations (usd per share)	(0.07)	0.71	(0.05)	1.05
Loss from discontinued operations, net of tax (usd per share)	0	0	0	0
Net (loss)/income (usd per share)	$ (0.07)	$ 0.71	$ (0.05)	$ 1.05
Weighted-average common shares outstanding:
Basic (in shares)	80,473	81,284	80,326	81,269
Diluted (in shares)	80,473	82,440	80,326	82,685