Stock-Based Compensation (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Stock options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Total intrinsic value of stock options exercised during the period	$ 1.3	$ 0.6
Unrecognized compensation expense related to unvested stock options	25.6
Expected weighted average period for recognizing unrecognized compensation expense	2 years 7 months 6 days
Performance shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Unrecognized compensation expense related to unvested stock options	$ 1.5
$3.03 to $3.29
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.03
Range of Exercise Prices upper range limit (in dollars per share)	$ 3.29
Number of Options outstanding (in shares)	180,188
Weighted Average Remaining Contractual Term	6 years 9 months
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 3.05
Number of Options exercisable (in shares)	131,810
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 3.04
$3.40 to $3.40
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.40
Range of Exercise Prices upper range limit (in dollars per share)	$ 3.40
Number of Options outstanding (in shares)	708,314
Weighted Average Remaining Contractual Term	7 years 5 months 12 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 3.40
Number of Options exercisable (in shares)	442,697
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 3.40
$3.60 to $6.90
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 3.60
Range of Exercise Prices upper range limit (in dollars per share)	$ 6.90
Number of Options outstanding (in shares)	605,545
Weighted Average Remaining Contractual Term	7 years 8 months 12 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 6.02
Number of Options exercisable (in shares)	327,413
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 5.91
$6.96 to $12.44
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 6.96
Range of Exercise Prices upper range limit (in dollars per share)	$ 12.44
Number of Options outstanding (in shares)	885,025
Weighted Average Remaining Contractual Term	7 years 7 months 24 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 11.05
Number of Options exercisable (in shares)	358,377
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 11.09
$12.58 to $12.58
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 12.58
Range of Exercise Prices upper range limit (in dollars per share)	$ 12.58
Number of Options outstanding (in shares)	577,550
Weighted Average Remaining Contractual Term	8 years 4 months 21 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 12.58
Number of Options exercisable (in shares)	25,000
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 12.58
$12.66 to $14.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 12.66
Range of Exercise Prices upper range limit (in dollars per share)	$ 14.65
Number of Options outstanding (in shares)	483,800
Weighted Average Remaining Contractual Term	8 years 9 months 7 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 13.91
Number of Options exercisable (in shares)	84,000
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 14.13
$14.81 to $16.07
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 14.81
Range of Exercise Prices upper range limit (in dollars per share)	$ 16.07
Number of Options outstanding (in shares)	583,650
Weighted Average Remaining Contractual Term	9 years 4 months 17 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 15.96
Number of Options exercisable (in shares)	28,175
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 15.62
$16.19 to $20.49
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 16.19
Range of Exercise Prices upper range limit (in dollars per share)	$ 20.49
Number of Options outstanding (in shares)	779,363
Weighted Average Remaining Contractual Term	8 years 9 months 7 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 19.49
Number of Options exercisable (in shares)	151,458
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 19.59
$21.09 to $21.21
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 21.09
Range of Exercise Prices upper range limit (in dollars per share)	$ 21.21
Number of Options outstanding (in shares)	3,000
Weighted Average Remaining Contractual Term	9 years 11 months 19 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 21.17
$21.54 to $21.54
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	$ 21.54
Range of Exercise Prices upper range limit (in dollars per share)	$ 21.54
Number of Options outstanding (in shares)	15,000
Weighted Average Remaining Contractual Term	8 years 9 months 22 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 21.54
Number of Options exercisable (in shares)	3,751
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 21.54

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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