Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenues	$ 1,066,421	$ 900,510	$ 2,015,946	$ 1,744,666
Costs and operating expenses:
Cost of revenues	522,203	456,967	991,164	884,647
Sales and marketing	141,566	107,832	270,493	214,422
General and administrative	191,355	168,462	372,754	334,366
Acquisition costs	26,402	15,594	29,427	52,130
Gains on asset sales	0	0	0	(5,242)
Total costs and operating expenses	881,526	748,855	1,663,838	1,480,323
Income from continuing operations	184,895	151,655	352,108	264,343
Interest income	4,437	841	7,529	1,766
Interest expense	(119,042)	(100,332)	(230,726)	(201,195)
Other income (expense)	1,284	1,555	1,621	(59,155)
Loss on debt extinguishment	(16,444)	(605)	(19,947)	(605)
Income from continuing operations before income taxes	55,130	53,114	110,585	5,154
Income tax expense	(9,325)	(13,812)	(22,718)	(3,179)
Net income from continuing operations	45,805	39,302	87,867	1,975
Net income from discontinued operations, net of tax	0	5,409	0	11,625
Net income	$ 45,805	$ 44,711	$ 87,867	$ 13,600
Earnings per share (EPS):
Basic EPS from continuing operations (in dollars per share)	$ 0.59	$ 0.56	$ 1.17	$ 0.03
Basic EPS from discontinued operations (in dollars per share)	0.00	0.08	0.00	0.17
Basic EPS (in dollars per share)	$ 0.59	$ 0.64	$ 1.17	$ 0.20
Weighted-average shares	77,923	69,729	75,383	68,931
Diluted EPS from continuing operations (in dollars per share)	$ 0.58	$ 0.56	$ 1.16	$ 0.03
Diluted EPS from discontinued operations (in dollars per share)	0.00	0.08	0.00	0.17
Diluted EPS (in dollars per share)	$ 0.58	$ 0.64	$ 1.16	$ 0.20
Weighted-average shares for diluted EPS	78,508	70,364	76,008	69,575
Quarterly cash dividend declared (in dollars per share)	$ 2	$ 1.75	$ 4	$ 3.5