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Stock-Based Compensation Plans (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Additional Stock-based Compensation Plans (Textual) [Abstract]
Cash received from option exercises and employee stock purchase plan purchases			$ 3,200,000	$ 3,000,000
Tax benefit realized for the tax deductions			700,000	1,100,000
Share-based Compensation	$ 4,200,000	$ 3,600,000	$ 7,886,000	$ 6,960,000
2007 Long Term Incentive Plan [Member]
Stock-based Compensation Plans (Textual) [Abstract]
Maximum number of shares available for issuance under the plan	7,500,000		7,500,000
2014 Long Term Incentive Plan [Member]
Stock-based Compensation Plans (Textual) [Abstract]
Maximum number of shares available for issuance under the plan	1,200,000		1,200,000
Expiry date for stock options grant	May 21, 2024
Shares available for granted under the incentive plan	1,764,044		1,764,044
Employee Stock Purchase Plan [Member]
Stock-based Compensation Plans (Textual) [Abstract]
Expiry date for stock options grant			Mar. 06, 2016
Shares authorized for issuance	3,500,000		3,500,000
Employee stock purchase price in percentage of fair market value	85.00%
Shares remaining in reserve for future issuance	563,138		563,138
Shares issued to employee under purchase plan	56,826	58,525
Weighted average fair value of employee stock purchase rights issued	$ 14.54	$ 13.40
Maximum [Member]
Stock-based Compensation Plans (Textual) [Abstract]
Range Of Forfeiture Provisions			5 years
Minimum [Member]
Stock-based Compensation Plans (Textual) [Abstract]
Range Of Forfeiture Provisions			6 months

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Employee service share based compensation tax benefit realized from exercise of stock options and vesting of restricted shares.

+ References

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- Definition

Employee common stock purchase price in percentage of fair market value.

+ References

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- Definition

Maximum number of shares available for issuance under the plan.

+ References

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- Definition

The total cash inflow associated with the amount received from employees to purchase company stock, including stock option exercises.

+ References

No definition available.

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Range of forfeiture provisions.

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- Definition

Shares remaining in reserve for future issuance.

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No definition available.

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Weighted average fair value of employee stock purchase rights issued.

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No definition available.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

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Date the equity-based award expires, in CCYY-MM-DD format.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

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

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

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

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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

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Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



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-Name Accounting Standards Codification

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-SubTopic 10

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-Paragraph 1

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-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770



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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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