Stock Option and Compensation Plans - Stock Compensation Expense (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Stock Option and Compensation Plans
Share-based compensation expense	$ 6,064	$ 8,332
Stock options \| Employees
Stock Option and Compensation Plans
Share-based compensation expense	4,400	6,100
Unrecognized share-based compensation costs for option awards, net of estimated forfeitures	$ 22,200
Expected weighted average period to recognize share-based compensation costs	2 years 6 months 1 day
Non-employee Options \| Consultants
Stock Option and Compensation Plans
Share-based compensation expense	$ 100	400
Unrecognized share-based compensation costs for option awards, net of estimated forfeitures	$ 400
Expected weighted average period to recognize share-based compensation costs	2 years 2 months 24 days
Restricted stock units
Stock Option and Compensation Plans
RSUs expected to vest (in shares)	366,000
Weighted average fair value of RSUs expected to vest (in dollars per share)	$ 30.62
Aggregate intrinsic value of RSUs expected to vest	$ 1,300
Number of shares granted (in shares)	233,000
Restricted stock units \| Employees
Stock Option and Compensation Plans
Share-based compensation expense	$ 1,300	$ 1,800
Expected weighted average period to recognize share-based compensation costs	2 years 7 months 2 days
Unrecognized compensation costs, net of estimated forfeitures	$ 9,600
Restricted stock units \| Consultants
Stock Option and Compensation Plans
Share-based compensation expense	$ 100
Expected weighted average period to recognize share-based compensation costs	2 years 5 months 22 days
Unrecognized compensation costs, net of estimated forfeitures	$ 200
Number of shares granted (in shares)		0
ESPP
Stock Option and Compensation Plans
Expected weighted average period to recognize share-based compensation costs	6 months
Shares of common stock issued under plan (in shares)	4,746	0
Number of shares available for future purchases under the plan (in shares)	995,254

Intrinsic value of equity-based compensation awards expected to vest. Excludes stock and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that are expected to vest in the future as of the reporting date.

+ References

No definition available.

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- Definition

Represents the weighted average fair value of equity awards, other than options, that are expected to vest as of the reporting date.

+ References

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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

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- Definition

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.

+ 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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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

No definition available.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

No definition available.

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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
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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

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- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

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