Shareholders' Equity and Stock Options (Details 1) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of changes in outstanding options
Weighted Average Options Price per Share, Beginning Balance	$ 15.13
Weighted Average Options Price per Share, Options Granted	$ 17.34
Weighted Average Options Price per Share, Options Vested	$ 13.81
Weighted Average Options Price per Share, Options Exercised	$ 11.77
Weighted Average Options Price per Share, Options Forfeited	$ 17.01
Weighted Average Options Price per Share, Options Expired	$ 19.67
Weighted Average Options Price per Share, Ending Balance	$ 14.73	$ 15.13
Options outstanding, Beginning Balance	2,600,583
Outstanding Options, Granted	296,188	313,000	361,456
Outstanding Options, Exercised	(389,089)	(136,290)	(263,206)
Outstanding Options, Forfeited	(42,193)
Outstanding Options, Expired	(582,550)
Options outstanding, Ending Balance	1,882,939	2,600,583
Vested and Exercisable, Beginning Balance	1,873,149
Vested and Exercisable, Vested	302,386
Vested and Exercisable, Exercisable	(389,089)
Vested and Exercisable, Forfeited	(42,193)
Vested and Exercisable, Expired	(582,550)
Vested and Exercisable, Ending Balance	1,161,703	1,873,149
Maximum [Member]
Summary of changes in outstanding options
Weighted Average Options Price per Share, Options Granted	$ 20.23
Range of Option Prices per Share, Beginning Balance	$ 21.64
Range of Option Prices per Share, Granted	$ 18.20
Range of Option Prices per Share, Vested	$ 17.71
Range of Option Prices per Share, Exercised	$ 19.16
Range of Option Prices per Share, Forfeited	$ 20.80
Range of Option Prices per Share, Expired	$ 21.64
Range of Option Prices per Share, Ending Balance	$ 20.23
Minimum [Member]
Summary of changes in outstanding options
Weighted Average Options Price per Share, Options Granted	$ 17.71
Range of Option Prices per Share, Beginning Balance	$ 6.91
Range of Option Prices per Share, Granted	$ 17.32
Range of Option Prices per Share, Vested	$ 6.91
Range of Option Prices per Share, Exercised	$ 6.91
Range of Option Prices per Share, Forfeited	$ 13.83
Range of Option Prices per Share, Expired	$ 18.76
Range of Option Prices per Share, Ending Balance	$ 6.91

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Share based compensation shares exercised under stock option plans exercise price range.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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.

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

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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