Stock-based Compensation (Summary of Stock Options Activity) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Shares
Outstanding at beginning of period (in shares)	261,936	377,907	570,762
Granted (in shares)	0	0	0
Exercised (in shares)	(24,334)	(96,921)	(172,521)
Forfeited (in shares)	(21,751)	(19,050)	(20,334)
Outstanding at end of period (in shares)	215,851	261,936	377,907
Options exercisable at end of period (in shares)	215,851	261,936	333,024
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 23.60	$ 22.62	$ 21.06
Granted (in dollars per share)	$ 0.00	$ 0.00	$ 0.00
Exercised (in dollars per share)	$ 20.20	$ 19.73	$ 17.39
Forfeited (in dollars per share)	$ 24.97	$ 23.79	$ 23.42
Outstanding at end of period (in dollars per share)	$ 23.85	$ 23.60	$ 22.62
Options exercisable at end of period (in dollars per share)	$ 23.85	$ 23.60	$ 23.16

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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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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

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

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

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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

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