Business Acquisitions - Summary of Company's Purchase Allocation Price (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition Purchase Price Allocation [Line Items]
Goodwill	$ 2,776,188,000us-gaap_Goodwill	$ 2,393,731,000us-gaap_Goodwill
Other intangible assets		29,600,000
Other long-term liabilities		(8,100,000)
13 Physician Group Practices Acquisition [Member]
Business Acquisition Purchase Price Allocation [Line Items]
Current assets	11,800,000
Property and equipment	3,800,000
Goodwill	389,600,000
Other intangible assets	124,800,000
Current liabilities	(14,400,000)
Deferred income tax liabilities-long-term	(26,300,000)
Other long-term liabilities	(700,000)
Total assets and liabilities	$ 488,600,000

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Amount of assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of deferred tax liability attributable to taxable temporary differences due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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