Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenues	$ 1,152,261	$ 924,676	$ 3,168,207	$ 2,669,342
Costs and operating expenses:
Cost of revenues	582,360	470,302	1,573,524	1,354,949
Sales and marketing	157,619	110,936	428,112	325,358
General and administrative	185,336	181,239	558,090	515,605
Acquisition costs	2,083	12,505	31,510	64,635
Impairment charges	0	7,698	0	7,698
Gains on asset sales	0	(27,945)	0	(33,187)
Total costs and operating expenses	927,398	754,735	2,591,236	2,235,058
Income from continuing operations	224,863	169,941	576,971	434,284
Interest income	2,291	762	9,820	2,528
Interest expense	(121,828)	(92,200)	(352,554)	(293,395)
Other income (expense)	(1,076)	2,938	545	(56,217)
Loss on debt extinguishment	(22,156)	(9,894)	(42,103)	(10,499)
Income from continuing operations before income taxes	82,094	71,547	192,679	76,701
Income tax expense	(2,194)	(22,778)	(24,912)	(25,957)
Net income from continuing operations	79,900	48,769	167,767	50,744
Net income from discontinued operations, net of tax	0	2,681	0	14,306
Net income	$ 79,900	$ 51,450	$ 167,767	$ 65,050
Earnings per share (EPS):
Basic EPS from continuing operations (in dollars per share)	$ 1.02	$ 0.69	$ 2.20	$ 0.73
Basic EPS from discontinued operations (in dollars per share)	0.00	0.04	0.00	0.21
Basic EPS (in dollars per share)	$ 1.02	$ 0.73	$ 2.20	$ 0.94
Weighted-average shares	78,055	71,190	76,283	69,689
Diluted EPS from continuing operations (in dollars per share)	$ 1.02	$ 0.68	$ 2.18	$ 0.72
Diluted EPS from discontinued operations (in dollars per share)	0.00	0.04	0.00	0.20
Diluted EPS (in dollars per share)	$ 1.02	$ 0.72	$ 2.18	$ 0.92
Weighted-average shares for diluted EPS	78,719	71,908	76,948	70,389
Cash dividends declared (in dollars per share)	$ 2	$ 1.75	$ 6	$ 5.25