Share-Based Compensation (Details Textuals) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Share-Based Compensation (Textuals) [Abstract]
Stock option granted	0
Aggregate intrinsic value of stock options exercised	$ 817,000
Actual tax benefit realized on options exercised	320,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0
Employee Stock Option [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost	2 years 329 days
Total unrecognized compensation cost	4,900,000
Compensation cost charged against income	604,000	474,000
Income tax benefit recognized during the period	236,000	186,000
Nonvested Stock Awards [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost	2 years 256 days
Total unrecognized compensation cost	16,000,000
Compensation cost charged against income	2,600,000	3,700,000
Income tax benefit recognized during the period	1,000,000	1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost	3 years 146 days
Total unrecognized compensation cost	4,000,000
Compensation cost charged against income	603,000	0
Income tax benefit recognized during the period	$ 236,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-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 g(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-Subparagraph b

-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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 14.F)

-URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

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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- Definition

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

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