Postretirement Benefit Plans (Target Allocations) (Details)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Equity securities
Defined Benefit Plan Disclosure
Actual allocation of plan assets	24.20%	22.50%
Minimum target allocation	20.00%
Maximum target allocation	40.00%
Fixed income
Defined Benefit Plan Disclosure
Actual allocation of plan assets	32.70%	31.50%
Minimum target allocation	20.00%
Maximum target allocation	60.00%
Hedge funds
Defined Benefit Plan Disclosure
Actual allocation of plan assets	31.70%	34.00%
Minimum target allocation	20.00%
Maximum target allocation	60.00%
Private equity
Defined Benefit Plan Disclosure
Actual allocation of plan assets	2.40%	3.10%
Minimum target allocation	0.00%
Maximum target allocation	15.00%
Cash and other
Defined Benefit Plan Disclosure
Actual allocation of plan assets	9.00%	8.90%
Minimum target allocation	0.00%
Maximum target allocation	30.00%

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2446-114920

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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