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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

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

Number of options outstanding, including both vested and non-vested options.

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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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Percentage of vesting of share-based compensation awards.

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Represents the period of commencement of vesting of awards from the date of grant.

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Stock-Based Compensation Plans (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	May 28, 2015	May 20, 2010	May 24, 2007	Jun. 30, 2006
The 2007 plan
Stock-based compensation plans
Number of shares authorized	2,800,000	2,800,000		800,000		2,000,000
Options
Options cancelled (in shares)	(155,745)
Outstanding at the end of the period (in shares)	555,388	555,388
1996 Plan
Stock-based compensation plans
Number of shares authorized							3,025,000
Vesting period		10 years
Vesting rate (as a percent)		25.00%
Period of beginning of vesting of awards from grant date		1 year
Total intrinsic value of options exercised (in dollars)		$ 0.3	$ 0.2
Options
Outstanding at the end of the period (in shares)	0	0
Employee Stock Purchase Plan
Stock-based compensation plans
Number of shares authorized					250,000
Restricted stock \| The 2007 plan
Stock-based compensation plans
Number of shares authorized	2,400,357	2,400,357