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Represents the number of shares of common stock the holder is entitled to receive upon vesting for each restricted stock unit held.

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Value, before forfeitures, of stock outstanding or other type of equity outstanding of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

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No definition available.

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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.

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

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No definition available.

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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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Percentage of vesting of share-based compensation awards.

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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).

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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).

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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.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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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).

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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.

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Gross number of share options (or share units) granted during the period.

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No definition available.

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

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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No definition available.

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Value, before forfeitures, of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Number of share options (or share units) exercised during the current period.

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

-Publisher SEC

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Stock-Based Compensation (Details) (USD $)	3 Months Ended		12 Months Ended
Stock-Based Compensation (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Employee Stock-Based Compensation Expense
Allocated Share-based Compensation Expense	$ 4,200,000	$ 4,400,000	$ 4,400,000
Weighted-average fair values and assumptions used in calculation of fair value
Dividend yield (as a percent)	0.00%	0.00%
Employee Stock Purchase Plan
Employee Stock Purchase Plan
Number of shares issued	0	0
Shares of common stock reserved for issuance under the ESPP	1,250,000
Shares of common stock available for future grant	759,738
Unrecognized compensation expense (in dollars)	229,000
Weighted-average period of recognition of unrecognized stock-based compensation expense	2 months
Employee Stock Options
Stock Option Grants
Options granted (in shares)	355,667	372,010
Stock Options
Stock Option Grants
Options exercised (in shares)	157,067	94,309
Options exercised (in dollars per share)	$ 15.14	$ 10.56
Stock Options \| Performance-Based Vesting
Stock Option Grants
Options granted (in shares)	0
Employee Stock Purchase Plan
Shares of common stock available for future grant	148,100
Employee Stock-Based Compensation Expense
Allocated Share-based Compensation Expense	119,000
Restricted Stock Units \| Performance-Based Vesting
Stock-based compensation
Granted (in shares)	22,980	44,630
Weighted-average grant date fair value (in dollars per share)	$ 31.12	$ 27.21
Stock outstanding (in shares)	29,133
Stock Option Grants
Options exercised (in shares)	4,227
Options exercised (in dollars per share)	$ 27.21
Stock awards other than options
Grant-date fair value (in dollars)	715,000	1,200,000
Grant-date fair value outstanding (in dollars)	883,000
Employee Stock-Based Compensation Expense
Allocated Share-based Compensation Expense	108,000
Restricted Stock Units \| Service-Based Vesting
Stock-based compensation
Granted (in shares)	359,616	331,253
Weighted-average grant date fair value (in dollars per share)	$ 31.14	$ 29.27
Stock awards other than options
Grant-date fair value (in dollars)	11,200,000	9,700,000
Number of shares of common stock to be received for each restricted stock unit	1
Shares of common stock issued in connection with the vesting of the stock award	156,838	164,532
Vested (in dollars per share)	$ 29.59	$ 27.98
Restricted Stock Units \| Employees \| Annual vesting over vesting period
Stock-based compensation
Vesting percentage	33.00%
Vesting period	3 years
Restricted Stock \| Outside directors
Stock-based compensation
Granted (in shares)	1,560	1,705
Weighted-average grant date fair value (in dollars per share)	$ 31.97	$ 29.27
Stock awards other than options
Grant-date fair value (in dollars)	$ 50,000	$ 50,000