Pension and Other Post-Retirement Benefits (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Expected required benefits 2015	$ 17,100,000
Expected required benefits 2016	13,900,000
Expected required benefits 2017	14,800,000
Expected required benefits 2018	17,000,000
Expected required benefits 2019	18,600,000
Expected required benefits, Thereafter	59,500,000
Maximum annual contribution per employee (as a percent)	6.00%
Employer matching contribution (as a percent)	50.00%
Expense for Company's matching contribution	2,000,000	1,600,000	1,500,000
Minimum
Defined Benefit Plan Disclosure [Line Items]
Maximum annual contribution per employee (as a percent)	1.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Maximum annual contribution per employee (as a percent)	75.00%
Bear Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17,700,000	19,400,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	323,493,000	351,869,000	328,726,000
Amortization period for pension plan actuarial gains (losses) (in years)	20 years
Amount of actuarial losses included in accumulated other comprehensive loss that is expected to be recognized in net periodic benefit cost	11,300,000
Amount of prior service cost included in accumulated other comprehensive loss that is expected to be recognized in net periodic benefit cost	0
Accumulated benefit obligation for all defined benefit pension plans	531,824,000	494,272,000	543,799,000
Expected required benefits 2015	34,961,000
Expected required benefits 2016	34,828,000
Expected required benefits 2017	34,660,000
Expected required benefits 2018	34,446,000
Expected required benefits 2019	34,195,000
Expected required benefits, Thereafter	164,091,000
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	0
Amount of actuarial losses included in accumulated other comprehensive loss that is expected to be recognized in net periodic benefit cost	0
Amount of prior service cost included in accumulated other comprehensive loss that is expected to be recognized in net periodic benefit cost	(100,000)
Accumulated benefit obligation for all defined benefit pension plans	1,356,000	1,084,000	4,208,000
Expected required benefits 2015	124,000
Expected required benefits 2016	118,000
Expected required benefits 2017	110,000
Expected required benefits 2018	104,000
Expected required benefits 2019	104,000
Expected required benefits, Thereafter	$ 399,000

Amortization Period for Pension Plan Actuarial Gains (Losses)

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- Definition

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503844

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)

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

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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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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.

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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.

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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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- 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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930

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Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

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Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Maximum amount the employee may contribute to a defined contribution plan.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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