Stockholder's Equity (Details 2) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stockholder's Equity
Number of shares issuable under the plan		1,400,000
Shares remaining to be issued	720,000
Restricted Stock Units
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 18	$ 15	$ 17
Granted (in dollars per share)	$ 31	$ 20	$ 16
Vested (in dollars per share)	$ 21	$ 15	$ 20
Forfeited (in dollars per share)	$ 25	$ 17	$ 18
Nonvested at the end of the period (in dollars per share)	$ 27	$ 18	$ 15
Shares
Nonvested at the beginning of the period (in shares)	260,734	223,224	248,951
Granted (in shares)	155,146	181,330	124,636
Vested (in shares)	(157,794)	(120,902)	(116,711)
Forfeited (in shares)	(12,334)	(22,918)	(33,652)
Nonvested at the end of the period (in shares)	245,752	260,734	223,224
Performance and Market Based Restricted Stock Units
Stockholder's Equity
Vesting period	4 years
Director [Member] \| Service Based Restricted Stock Units
Stockholder's Equity
Vesting period	3 years

Aggregate number of common shares reserved for future issuance.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

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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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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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-Name Accounting Standards Codification

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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 of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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 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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