Equity Plans Stock Option Activity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Options, Outstanding [Roll Forward]
Outstanding Shares as of January 1, 2012	85,526
Exercised, shares	(20,982)
Outstanding Shares as of December 31, 2012	64,544	85,526
Options exercisable at December 31, 2012, shares	64,544
Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding as of January 1, 2012, wtd avg exercise price	$ 18.24
Exercised, wtd avg exercise price	$ 15.18
Outstanding as of December 31, 2012, wtd avg exercise price	$ 19.24	$ 18.24
Options exercisable at December 31, 2012, wtd avg exercise price	$ 19.24
Weighted average remaining contractual term of options outstanding	1 year 11 months 1 day	2 years 8 months 23 days
Options exercisable at December 31, 2012, wtd avg remaining contractual term	1 year 11 months 1 day
Options outstanding, intrinsic value	$ 490	$ 518
Option exercises in period, total intrinsic value	210	0	133
Options exercisable at December 31, 2012, intrinsic value	$ 490
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option award vesting period	4 years
Option award exercise period	10 years
Employee Stock Option [Member] \| Annual [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual option vesting percentage	25.00%

Percentage of vesting of share-based compensation awards.

No definition available.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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

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

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

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