Stockholders' Equity - Performance-Based Restricted Stock Units (Details)	12 Months Ended
Dec. 31, 2016 USD ($) company $ / shares shares	Dec. 31, 2015 USD ($) company $ / shares shares
Weighted average exercise price of nonvested restricted stock award and units
Vesting period	3 years
Performance Based Restricted Stock Units (“PSUs”)
Assumptions used for estimating value of awards granted
Outstanding, beginning of period (in shares) \| shares	36,938
Awarded (in shares) \| shares	69,691	43,900
Forfeited (in shares) \| shares	(3,652)	(6,962)
Outstanding, end of period (in shares) \| shares	102,977	36,938
Estimated fair value \| $	$ 97.22	$ 85.00
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share) \| $ / shares	$ 85.00
Awarded (in dollars per share) \| $ / shares	97.22	$ 85.00
Forfeited (in dollars per share) \| $ / shares	91.89	85.00
Outstanding, end of period (in dollars per share) \| $ / shares	$ 93.03	$ 85.00
Unrecognized compensation expense \| $	$ 6,100,000
Unrecognized compensation expense, period of recognition	1 year 11 months 19 days
Expected dividend yield (as a percent)	0.00%	0.00%
Risk-free interest rate (as a percent)	1.00%	1.00%
Expected volatility, minimum (as a percent)	16.00%	15.00%
Expected volatility, maximum (as a percent)	81.00%	52.00%
Expected volatility, average (as a percent)	32.00%	28.00%
Vesting period	3 years	3 years
Number of trading days considered for average share value	30	30
Number of companies in peer group \| company	56	54
Nonvested restricted stock awards and units
Unrecognized compensation expense \| $	$ 6,100,000
Unrecognized compensation expense, period of recognition	1 year 11 months 19 days
Performance Based Restricted Stock Units (“PSUs”) \| Minimum
Weighted average exercise price of nonvested restricted stock award and units
Percentage of shares to be settled	0.00%	0.00%
Performance Based Restricted Stock Units (“PSUs”) \| Maximum
Weighted average exercise price of nonvested restricted stock award and units
Percentage of shares to be settled	200.00%	200.00%

Represents the number of companies in peer group considered for S&P Health Care Services Industry Index.

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The estimated fair value of share-based awards for which the share vested and gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

No definition available.

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Percentage of shares to be settled as per peer group of share-based compensation awards.

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Threshold number of specified trading days that common stock price to be considered for average share value for share based compensation during the performance period.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Subparagraph (c)(2)(iii)(1)
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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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No definition available.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average expected volatility rate of share-based compensation awards.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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