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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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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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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No definition available.

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

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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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Stock-Based Compensation - Range of Exercise Prices (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Total intrinsic value of stock options exercised during the period	$ 4.7	$ 2.5	$ 2.7
Unrecognized compensation expense related to unvested stock options	$ 26.9
Expected weighted average period for recognizing unrecognized compensation expense	2 years 6 months
Performance shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Unrecognized compensation expense related to unvested stock options	$ 1.2
$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)	153,878
Weighted Average Remaining Contractual Term	5 years 7 months 13 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 3.05
Number of Options exercisable (in shares)	152,017
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 3.05
$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	6 years 8 months 9 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 3.40
Number of Options exercisable (in shares)	531,236
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)	583,542
Weighted Average Remaining Contractual Term	6 years 10 months 24 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 6.01
Number of Options exercisable (in shares)	389,433
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 5.90
$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)	693,090
Weighted Average Remaining Contractual Term	7 years 4 months 13 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 11.36
Number of Options exercisable (in shares)	378,156
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 11.35
$12.58 to $14.20
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)	$ 14.20
Number of Options outstanding (in shares)	527,974
Weighted Average Remaining Contractual Term	8 years 4 months 10 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 12.78
Number of Options exercisable (in shares)	189,989
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 12.76
$14.24 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)	14.24
Range of Exercise Prices upper range limit (in dollars per share)	$ 16.07
Number of Options outstanding (in shares)	768,900
Weighted Average Remaining Contractual Term	8 years 5 months 23 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 15.36
Number of Options exercisable (in shares)	161,331
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 14.46
$16.09 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)	16.09
Range of Exercise Prices upper range limit (in dollars per share)	$ 20.49
Number of Options outstanding (in shares)	782,624
Weighted Average Remaining Contractual Term	8 years 5 months 16 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 19.28
Number of Options exercisable (in shares)	183,354
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 19.52
$20.92 to $22.14
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	20.92
Range of Exercise Prices upper range limit (in dollars per share)	$ 22.14
Number of Options outstanding (in shares)	106,300
Weighted Average Remaining Contractual Term	9 years 1 month 21 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 21.54
Number of Options exercisable (in shares)	5,625
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 21.54
$22.76 to $22.76
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	22.76
Range of Exercise Prices upper range limit (in dollars per share)	$ 22.76
Number of Options outstanding (in shares)	793,000
Weighted Average Remaining Contractual Term	9 years 4 months 17 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 22.76
$22.84 to $27.38
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)	22.84
Range of Exercise Prices upper range limit (in dollars per share)	$ 27.38
Number of Options outstanding (in shares)	156,100
Weighted Average Remaining Contractual Term	9 years 4 months 28 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 23.76