Stock-Based Compensation Plans (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Summary of the changes in outstanding stock options
Stock Options Outstanding at December 31, 2011	4,590
Stock options, Granted	861
Stock options, Exercised	(924)
Stock options, Forfeited	(327)
Stock Options Outstanding at September 30, 2012	4,200	4,590
Options exercisable, Shares	1,642
Weighted Average Exercise Price, Outstanding at December 31, 2011	$ 25.83
Weighted Average Exercise Price / Share, Granted	$ 26.57
Weighted Average Exercise Price / Share, Exercised	$ 24.03
Weighted Average Exercise Price / Share, Forfeited	$ 27.85
Weighted Average Exercise Price, Outstanding at September 30, 2012	$ 26.22	$ 25.83
Options exercisable, Weighted Average Exercise Price	$ 25.49
Weighted Average Remaining Contractual Term, Outstanding	6 years 6 months	5 years 4 months 24 days
Weighted Average Remaining Contractual Term, Options Granted	10 years
Weighted Average Remaining Contractual Term, Options Exercised	1 month 6 days
Weighted Average Remaining Contractual Term, Options Forfeited	6 years 8 months 12 days
Weighed average remaining contractual term, Options exercisable	2 years 7 months 6 days

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c), d(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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.