Pension and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Health care cost trend rate assumed for next fiscal year	7.50%
Ultimate health care cost trend rate	5.00%
Estimated nonqualified benefits in next fiscal year	$ 1,573
Estimated future employer contributions in next fiscal year	40,000
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	100.00%	100.00%
Target allocation range, maximum	100.00%	100.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	423,167
Balance, end of year	470,165	423,167
Equity Securities US
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	9.00%	10.00%
Target allocation range, minimum	3.00%	3.00%
Target allocation range, maximum	15.00%	15.00%
Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	17,092	20,176
Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	26,739	22,923
Equity Securities International
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	9.00%	9.00%
Target allocation range, minimum	3.00%	3.00%
Target allocation range, maximum	15.00%	15.00%
Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	946	1,101
Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	43,710	38,246
Fixed Income Investments US
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	61.00%	56.00%
Target allocation range, minimum	35.00%	35.00%
Target allocation range, maximum	75.00%	75.00%
Corporate debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	128,033	108,844
US government debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	52,674	38,870
Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	104,324	86,672
Fixed Income Investments, Foreign [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	6.00%	6.00%
Target allocation range, minimum	3.00%	3.00%
Target allocation range, maximum	10.00%	10.00%
Foreign Corporate Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	27,784	23,920
Absolute Return
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	7.00%	9.00%
Target allocation range, minimum	5.00%	5.00%
Target allocation range, maximum	15.00%	15.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	39,448
Balance, end of year	33,021	39,448
Real assets
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	5.00%	5.00%
Target allocation range, minimum	3.00%	3.00%
Target allocation range, maximum	10.00%	10.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	23,192
Balance, end of year	24,116	23,192
Private equity
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	1.00%	1.00%
Target allocation range, minimum	0.00%	0.00%
Target allocation range, maximum	3.00%	3.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	3,793
Balance, end of year	3,682	3,793
Short-term Investments
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Actual Allocation	2.00%	4.00%
Target allocation range, minimum	0.00%	0.00%
Target allocation range, maximum	3.00%	3.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	15,982
Balance, end of year	8,044	15,982
Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	318,044	265,082
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	17,092	20,176
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	18,006	11,169
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	946	1,101
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	43,710	38,246
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Corporate debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	128,033	108,844
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| US government debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	52,674	38,870
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	29,799	22,756
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Foreign Corporate Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	27,784	23,920
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Absolute Return
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Real assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Quoted Prices in Active Markets for Identical Inputs (Level 1) \| Short-term Investments
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	98,900	100,107
Significant Other Observable Inputs (Level 2) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	8,733	11,754
Significant Other Observable Inputs (Level 2) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Corporate debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| US government debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	74,525	63,916
Significant Other Observable Inputs (Level 2) \| Foreign Corporate Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Absolute Return
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Real assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	7,598	8,455
Significant Other Observable Inputs (Level 2) \| Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Other Observable Inputs (Level 2) \| Short-term Investments
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	8,044	15,982
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	53,221	57,978
Significant Unobservable Inputs (Level 3) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Corporate stocks
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Corporate debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| US government debt
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Foreign Corporate Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Significant Unobservable Inputs (Level 3) \| Absolute Return
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	33,021	39,448
Significant Unobservable Inputs (Level 3) \| Real assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	16,518	14,737
Significant Unobservable Inputs (Level 3) \| Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	3,682	3,793
Significant Unobservable Inputs (Level 3) \| Short-term Investments
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, end of year	0	0
Pension Benefits
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	22,205	24,119	22,215
Interest cost	26,817	23,914	24,896
Expected return on plan assets	(26,624)	(23,909)	(23,670)
Net actuarial loss	17,639	26,371	21,116
Prior service cost (gain)	952	1,375	1,380
Settlement loss	789	0	0
Net periodic benefit cost	41,778	51,870	45,937
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.87%	3.95%	4.75%
Expected return on plan assets	6.25%	6.00%	6.25%
Rate of compensation increase	4.25%	4.25%	4.50%
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2015	41,454
2016	42,052
2017	39,730
2018	40,525
2019	43,292
After 2019	231,790
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	423,167	430,894
Realized gains/(losses)	55,450	(250)
Balance, end of year	470,165	423,167	430,894
Pension Benefits \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	57,978	82,555
Realized gains/(losses)	510	6,568
Unrealized gains/(losses)	4,334	(2,172)
Purchases	407	30,900
Sales	(10,008)	(59,873)
Balance, end of year	53,221	57,978
Pension Benefits \| Significant Unobservable Inputs (Level 3) \| Commingled funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year		22,063
Realized gains/(losses)		5,721
Unrealized gains/(losses)		(6,629)
Purchases		0
Sales		(21,155)
Balance, end of year		0
Pension Benefits \| Significant Unobservable Inputs (Level 3) \| Absolute Return
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	39,448	37,289
Realized gains/(losses)	386	831
Unrealized gains/(losses)	1,837	2,344
Purchases	0	30,900
Sales	(8,650)	(31,916)
Balance, end of year	33,021	39,448
Pension Benefits \| Significant Unobservable Inputs (Level 3) \| Real assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	14,737	12,702
Realized gains/(losses)	48	16
Unrealized gains/(losses)	2,065	2,127
Purchases	48	0
Sales	(380)	(108)
Balance, end of year	16,518	14,737
Pension Benefits \| Significant Unobservable Inputs (Level 3) \| Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	3,793	3,807
Realized gains/(losses)	76	0
Unrealized gains/(losses)	432	(14)
Purchases	359	0
Sales	(978)	0
Balance, end of year	3,682	3,793
Pension Benefits \| Significant Unobservable Inputs (Level 3) \| Short-term Investments
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year		6,694
Realized gains/(losses)		0
Unrealized gains/(losses)		0
Purchases		0
Sales		(6,694)
Balance, end of year		0
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	2,454	2,644	2,336
Interest cost	3,338	2,873	3,355
Expected return on plan assets	0	0	0
Net actuarial loss	1,267	1,794	1,719
Prior service cost (gain)	(2,181)	(2,181)	(2,181)
Settlement loss	0	0	0
Net periodic benefit cost	4,878	5,130	5,229
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.34%	3.51%	4.25%
Expected return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	0.00%	0.00%	0.00%
Health care cost trend rate assumed for next fiscal year	7.50%
Ultimate health care cost trend rate	5.00%
Year that rate reaches ultimate trend rate	2019
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2015	7,936
2016	8,832
2017	9,772
2018	10,928
2019	12,058
After 2019	81,416
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	0	0
Realized gains/(losses)	0	0
Balance, end of year	$ 0	$ 0	$ 0

Defined Benefit Plan, Assets, Purchases

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- Definition

Amount of employer's best estimate of funding expected to be paid for nonqualified pension benefits during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

No definition available.

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- Definition

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

-URI http://asc.fasb.org/extlink&oid=6504192

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

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-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost)

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Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

+ 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 (d)(iv)(02)(A)

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- Definition

The amount of gains or losses recognized in net periodic benefit cost.

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

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- Definition

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

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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

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-Section 50

-Paragraph 1

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- Definition

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

+ References

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- Definition

The amount of decrease in the plan assets attributed to the sale, liquidation, spin-off or other divestiture of a corporate division or subsidiary.

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

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-Name Accounting Standards Codification

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-SubTopic 60

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-Section 50

-Paragraph 1

-Subparagraph (h)(3)

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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Amount of net gain (loss) recognized in net periodic benefit cost as a result of an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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Target allocation maximum percentage of investments of this type to total plan assets presented on a weighted average basis.

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Target allocation minimum percentage of investments of this type to total plan assets presented on a weighted average basis.

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- Definition

The ultimate trend rate for health care costs.

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Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

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Year the ultimate health care cost trend rate is expected to be reached, in CCYY format.

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