Postretirement Benefits (Details 2)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee pension plan
Actuarial assumptions used to determine benefit obligations:
Discount rate (as a percent)	4.17%	5.11%	4.19%	4.99%
Compensation increases (as a percent)	3.32%	4.15%	4.15%	4.15%
Actuarial assumptions used to determine net periodic benefit cost:
Discount rate (as a percent)	5.11%	4.19%	4.99%
Expected return on assets (as a percent)	7.00%	7.50%	7.50%	8.00%
Rate of compensation increase (as a percent)	4.15%	4.15%	4.15%
Supplemental employee retirement plan (SERP)
Actuarial assumptions used to determine benefit obligations:
Pre-retirement discount rate (as a percent)	4.17%	5.11%	4.19%	4.99%
Post-retirement discount rate (as a percent)	3.67%	4.61%	3.69%	4.49%
Compensation increases (as a percent)	5.00%	6.00%	6.00%	6.00%
Actuarial assumptions used to determine net periodic benefit cost:
Pre-retirement discount rate (as a percent)	5.11%	4.19%	4.99%
Post-retirement discount rate (as a percent)	4.61%	3.69%	4.49%
Rate of compensation increase (as a percent)	6.00%	6.00%	6.00%

The post-retirement interest rate used to adjust for the time value of money for the plan.

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- Definition

The pre-retirement interest rate used to adjust for the time value of money for the plan.

+ References

No definition available.

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- Definition

The post-retirement interest rate used to adjust for the time value of money.

+ References

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- Definition

The pre-retirement interest rate used to adjust for the time value of money.

+ References

No definition available.

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- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(2)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

The interest rate used to adjust for the time value of money.

+ References

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(2)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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