Stock-Based Compensation (Schedule of Other Information about Stock Options) (Details) (Stock Option Awards [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock Option Awards [Member]
Weighted-average estimated grant-date fair value of employee stock options granted	$ 28.96		$ 28.23
Pre tax intrinsic values of stock options exercised, total	$ 2,903	$ 1,897	$ 7,435	$ 8,230
Pre-tax unrecognized compensation expense, net of estimated forfeitures as of June 30, 2011	$ 5,115		$ 5,115
Weighted-average period (in years) to be recognized as expense			2.1

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(2)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration