Share-Based Payments (Details Textual)	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance multiplier	0.5
Number of days for calculation of average closing stock price	30 days
Shares issued under ESPP	74,000	112,000
Market stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equal annual increments	3
Minimum target number of market stock units granted based on stock performance in percent	0.00%
Maximum target number of market stock units granted based on stock performance in percent	200.00%
Performance units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equal annual increments	3
Minimum target number of market stock units granted based on stock performance in percent	0.00%
Maximum target number of market stock units granted based on stock performance in percent	200.00%

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Minimum target number of market stock units granted based on stock performance in percent.

+ References

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Number of days for calculation of average closing stock price.

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Number of equal annual increments.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Performance Multiplier Threshold

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- Definition

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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