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.

Reference 1: 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=49178875&loc=d3e12355-114930

Reference 2: 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=58740216&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Pension Benefit and Retirement Health and Life Insurance Benefits (Fair Value of Net Assets by Asset Category) (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 171,007	$ 170,600	$ 171,218
Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Pension assets	6,782	5,204
Fixed income bonds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	110,427	102,535
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	43,454	51,097
Guaranteed deposit account
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 10,344	$ 11,764