Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues	$ 4,368,428	$ 3,611,989	$ 2,725,867
Costs and operating expenses:
Cost of revenues	2,193,149	1,820,870	1,291,506
Sales and marketing	581,724	438,742	332,012
General and administrative	745,906	694,561	493,284
Acquisition costs	38,635	64,195	41,723
Impairment charges	0	7,698	0
Gain on asset sales	0	(32,816)	0
Total costs and operating expenses	3,559,414	2,993,250	2,158,525
Income from operations	809,014	618,739	567,342
Interest income	13,075	3,476	3,581
Interest expense	(478,698)	(392,156)	(299,055)
Other income (expense)	9,213	(57,924)	(60,581)
Loss on debt extinguishment	(65,772)	(12,276)	(289)
Income from continuing operations before income taxes	286,832	159,859	210,998
Income tax expense	(53,850)	(45,451)	(23,224)
Net income from continuing operations	232,982	114,408	187,774
Net income from discontinued operations, net of tax	0	12,392	0
Net income	$ 232,982	$ 126,800	$ 187,774
Earnings per share (EPS):
Basic EPS from continuing operations (in dollars per share)	$ 3.03	$ 1.63	$ 3.25
Basic EPS of discontinued operations (in dollars per share)	0.00	0.18	0.00
Basic EPS (in dollars per share)	$ 3.03	$ 1.81	$ 3.25
Weighted-average shares	76,854	70,117	57,790
Dilutive EPS from continuing operations (in dollars per share)	$ 3.00	$ 1.62	$ 3.21
Dilutive EPS from discontinued operations (in dollars per share)	0.00	0.17	0.00
Diluted EPS (in dollars per share)	$ 3.00	$ 1.79	$ 3.21
Weighted-average shares	77,535	70,816	58,483
Dividends declared per share (in dollars per share)	$ 8	$ 7	$ 17.71