Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-SubTopic 30
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-Paragraph 6
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Date the declared dividend will be paid, in CCYY-MM-DD format.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
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Date the dividend to be paid was declared, in CCYY-MM-DD format.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Feb. 13, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Cash dividends declared (in USD per share)			$ 0.66	$ 0.60	$ 0.57
Pension Benefits [Member]
Subsequent Event [Line Items]
Final contribution to fund benefit obligation			$ 43,075	$ 48,844	$ 33,990
Settlement of remaining benefit obligation			7,438	0
Pension Benefits [Member] \| US Plan [Member]
Subsequent Event [Line Items]
Final contribution to fund benefit obligation			18,084	25,644	$ 26,188
Settlement of remaining benefit obligation			$ 7,438	$ 0
Pension Benefits [Member] \| Scenario Forecast [Member] \| US Plan [Member]
Subsequent Event [Line Items]
Final contribution to fund benefit obligation		$ 1,300
Settlement of remaining benefit obligation		18,700
Additional settlement loss		$ 5,300
Subsequent Event [Member]
Subsequent Event [Line Items]
Cash dividends declared (in USD per share)	$ 0.17
Dividend declaration date	Feb. 13, 2018
Dividend payable date	Apr. 03, 2018
Dividend record date	Mar. 19, 2018