Consolidated Statements of Comprehensive Income Parenthetical - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Amortization of actuarial loss, tax	$ 184	$ 613
Effect of settlements, tax	$ 114	$ 192

Amount of tax expense (benefit) related to gain (loss) adjustment to other comprehensive income (loss) resulting from settlement or curtailment of pension and other postretirement defined benefit plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Settlement of a Pension or Postretirement Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6531942

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Plan Curtailment
-URI http://asc.fasb.org/extlink&oid=6520938

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration