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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 08, 2015
Summary Of Significant Accounting Policies [Line Items] |  |  |
Cash and cash equivalents maturity description | 90 days or less |  |
Additional amounts to be paid in cash or common stock based on achievement of performance measures within period, maximum years | 5 years |  |
Money market funds fair value | $ 12.4 | $ 13.9 |
Cash surrender fair value of life insurance | 15.8 | 14.5 |
Contingent consideration liabilities related to acquisitions, fair value | $ 17.3 | $ 24.9 |
5.25% Senior Unsecured Notes Due 2023 [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Debt instrument interest rate |  |  | 5.25%
Variable Interest Entity, Primary Beneficiary [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Consolidation method ownership percentage in joint venture | 75.00% |  |
Unnamed Corporate Joint Venture [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Equity method ownership percentage in joint venture | 37.50% |  |
Government Contracts Concentration Risk [Member] | Accounts Receivable [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Percentage of net accounts receivable | 17.00% | 19.00% |
Buildings [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 20 years |  |
Maximum [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Long-term investments maturity period, in years | 7 years |  |
Short-Term investments maturity period, in years | 1 year |  |
Intangible assets finite lives | 20 years |  |
Maximum [Member] | Medical Equipment [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 7 years |  |
Maximum [Member] | Computer Equipment [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 7 years |  |
Maximum [Member] | Software and Software Development Costs [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 7 years |  |
Maximum [Member] | Furniture [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 7 years |  |
Minimum [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Long-term investments maturity period, in years | 1 year |  |
Intangible assets finite lives | 1 year |  |
Minimum [Member] | Medical Equipment [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 3 years |  |
Minimum [Member] | Computer Equipment [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 3 years |  |
Minimum [Member] | Software and Software Development Costs [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 3 years |  |
Minimum [Member] | Furniture [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Property and equipment estimated useful lives, years | 3 years |  |

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