CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 830,555	$ 1,033,082	$ 427,410
Adjustments to reconcile net income to net cash provided by operating activities:
(Gain) loss on settlements, net	(526,827)	0	495,000
Depreciation and amortization	777,485	720,252	638,024
Impairment charges	981,589	296,408	210,234
Debt redemption charges	0	0	48,072
Stock-based compensation expense	35,092	38,338	56,664
Deferred income taxes	(395,217)	52,010	61,744
Equity investment income, net	28,925	17,766	9,293
Gain on sales of business interests, net	(23,402)	(404,165)	0
Other non-cash charges, net	66,925	(7,338)	44,691
Changes in operating assets and liabilities, net of effect of acquisitions and divestitures:
Accounts receivable	(156,305)	(152,240)	(202,867)
Inventories	(18,625)	22,920	(48,313)
Other receivables and other current assets	(117,154)	(54,038)	32,761
Other long-term assets	(11,945)	35,893	3,723
Accounts payable	26,876	11,897	30,998
Accrued compensation and benefits	(78,239)	68,272	54,950
Other current liabilities	1,908	176,494	113,470
Settlement receipts (payments)	526,827	0	(493,775)
Income taxes	(52,176)	77,376	41,767
Other long-term liabilities	11,157	30,517	33,354
Net cash provided by operating activities	1,907,449	1,963,444	1,557,200
Cash flows from investing activities:
Additions of property and equipment	(905,250)	(829,095)	(707,998)
Acquisitions	(803,879)	(563,856)	(96,469)
Proceeds from asset and business sales	92,336	64,725	19,715
Purchase of investments available for sale	(13,117)	(13,539)	(8,783)
Purchase of investments held-to-maturity	(230,989)	(1,133,192)	(1,709,883)
Proceeds from sale of investments available for sale	6,408	18,963	2,058
Proceeds from investments held-to-maturity	492,470	1,240,502	1,637,358
Purchase of equity investments	(4,816)	(27,096)	(17,911)
Proceeds from sale of equity investments	0	40,920	0
Distributions received on equity investments	106	0	129
Net cash used in investing activities	(1,366,731)	(1,201,668)	(881,784)
Cash flows from financing activities:
Borrowings	50,991,960	51,991,490	54,541,988
Payments on long-term debt and other financing costs	(50,837,112)	(52,116,120)	(53,998,962)
Purchase of treasury stock	(802,949)	(1,097,822)	(549,935)
Distributions to noncontrolling interests	(211,467)	(192,401)	(174,635)
Stock award exercises and other share issuances, net	21,252	23,543	26,155
Excess tax benefits from stock award exercises	0	13,251	28,157
Contributions from noncontrolling interests	74,552	47,590	54,644
Proceeds from sales of additional noncontrolling interests	2,864	0	0
Purchases of noncontrolling interests	(5,357)	(21,512)	(66,382)
Net cash used in financing activities	(766,257)	(1,351,981)	(138,970)
Effect of exchange rate changes on cash and cash equivalents	254	4,276	(2,571)
Net (decrease) increase in cash and cash equivalents	(225,285)	(585,929)	533,875
Less: Net (decrease) increase in cash and cash equivalents from discontinued operations	(58,743)	(15,788)	25,855
Net (decrease) increase in cash and cash equivalents from continuing operations	(166,542)	(570,141)	508,020
Cash and cash equivalents of continuing operations at beginning of the year	674,776	1,244,917	736,897
Cash and cash equivalents of continuing operations at end of the year	$ 508,234	$ 674,776	$ 1,244,917