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Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification adjustment for (gain) loss on derivative instruments included in net income (loss), tax	$ 224	$ 226	$ 233
Postretirement liability gains (losses) arising during the period, tax	(1,162)	(836)	(55)
Amortization of postretirement liability (gains) losses included in net periodic benefit cost (credit), tax	645	1,425	1,128
Reclassification of postretirement liability adjustment to regulatory asset, tax	(876)	0	1,416
Foreign currency translation adjustment recognized during the period, tax	(3)	31	(105)
Reclassification adjustment for (gain) loss on foreign currency translation adjustment included in net income (loss), tax	0	0	490
Net unrealized gains (losses) on available-for-sale investments arising during the period, tax	(75)	(98)	(91)
Reclassification adjustments for (gain) loss on available-for-sale investments included in net income (loss), tax	$ 65	$ 77	$ 70

X

- Definition

Other comprehensive (income) loss, reclassification adjustment from AOCI, postretirement liability adjustment to regulatory asset, tax.

+ References

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Amount of tax expense (benefit), before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 20
-Subparagraph (c)
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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for translation gain (loss) realized upon the sale or liquidation of an investment in a foreign entity and foreign currency hedges that are designated and qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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Amount, before reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

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Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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