Supplemental Data - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ (96,668)	$ (172,034)	$ 434,883	$ 489,876
Changes in operating and intercompany assets and liabilities and non-cash items included in net income			947,365	1,078,274
Net cash provided by operating activities			1,382,248	1,568,150
Cash flows from investing activities:
Additions of property and equipment	(231,682)	(240,889)	(705,659)	(639,829)
Acquisitions			(113,526)
Proceeds from asset and business sales			135,268	92,529
Investments and other items			22,598	168,289
Net cash used in investing activities			(661,319)	(1,105,549)
Cash flows from financing activities:
Long-term debt			845,836	(108,463)
Intercompany			0	0
Other items			(1,269,175)	(421,369)
Net cash used in financing activities			(423,339)	(529,832)
Effect of exchange rate changes on cash, cash equivalents and restricted cash			(5,790)	5,449
Net decrease in cash, cash equivalents and restricted cash from continuing operations			291,800	(61,782)
Cash, cash equivalents and restricted cash of continuing operations at beginning of the year			518,920	683,463
Cash, cash equivalents and restricted cash of continuing operations at end of the period	540,155	$ 538,987	540,155	538,987
Physician Groups
Cash flows from operating activities:
Net income (loss)			20,773
Changes in operating and intercompany assets and liabilities and non-cash items included in net income			77,229
Net cash provided by operating activities			98,002
Cash flows from investing activities:
Additions of property and equipment			(2,575)
Acquisitions			0
Proceeds from asset and business sales			0
Investments and other items			(1)
Net cash used in investing activities			(2,576)
Cash flows from financing activities:
Long-term debt			0
Intercompany			77,286
Other items			0
Net cash used in financing activities			77,286
Effect of exchange rate changes on cash, cash equivalents and restricted cash			0
Net decrease in cash, cash equivalents and restricted cash from continuing operations			172,712
Cash, cash equivalents and restricted cash of continuing operations at beginning of the year			0
Cash, cash equivalents and restricted cash of continuing operations at end of the period	0		0
Unrestricted Subsidiaries
Cash flows from operating activities:
Net income (loss)			298
Changes in operating and intercompany assets and liabilities and non-cash items included in net income			(298)
Net cash provided by operating activities			0
Cash flows from investing activities:
Additions of property and equipment			0
Acquisitions			0
Proceeds from asset and business sales			0
Investments and other items			0
Net cash used in investing activities			0
Cash flows from financing activities:
Long-term debt			0
Intercompany			0
Other items			0
Net cash used in financing activities			0
Effect of exchange rate changes on cash, cash equivalents and restricted cash			0
Net decrease in cash, cash equivalents and restricted cash from continuing operations			0
Cash, cash equivalents and restricted cash of continuing operations at beginning of the year			0
Cash, cash equivalents and restricted cash of continuing operations at end of the period	0		0
Company and Restricted Subsidiaries
Cash flows from operating activities:
Net income (loss)			413,812
Changes in operating and intercompany assets and liabilities and non-cash items included in net income			870,434
Net cash provided by operating activities			1,284,246
Cash flows from investing activities:
Additions of property and equipment			(703,084)
Acquisitions			(113,526)
Proceeds from asset and business sales			135,268
Investments and other items			22,599
Net cash used in investing activities			(658,743)
Cash flows from financing activities:
Long-term debt			845,836
Intercompany			(77,286)
Other items			(1,269,175)
Net cash used in financing activities			(500,625)
Effect of exchange rate changes on cash, cash equivalents and restricted cash			(5,790)
Net decrease in cash, cash equivalents and restricted cash from continuing operations			119,088
Cash, cash equivalents and restricted cash of continuing operations at beginning of the year			518,920
Cash, cash equivalents and restricted cash of continuing operations at end of the period	$ 540,155		540,155
Discontinued Operations
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			270,565	82,694
Discontinued Operations | Physician Groups
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			172,712
Discontinued Operations | Unrestricted Subsidiaries
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			0
Discontinued Operations | Company and Restricted Subsidiaries
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			97,853
Continuing Operations
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			21,235	$ (144,476)
Continuing Operations | Physician Groups
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			0
Continuing Operations | Unrestricted Subsidiaries
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			0
Continuing Operations | Company and Restricted Subsidiaries
Cash flows from financing activities:
Net decrease in cash, cash equivalents and restricted cash from continuing operations			$ 21,235