Benefit Plans Benefit Plans (Detail 10) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Actual return on plan assets:
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Sold		$ (2,857)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	$ 36,883	(26,946)
Defined Benefit Plan, Fair Value of Plan Assets	919,782	820,272	$ 844,715
Fair Value, Inputs, Level 3 [Member]
Actual return on plan assets:
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held	21	25
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Sold	0
Defined Benefit Plan Sales, Total	5,809
Defined Benefit Plan, Purchases, Total	108	(21,316)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	300	(3,830)
Defined Benefit Plan, Fair Value of Plan Assets	1,514	6,894	34,872
Real Asset Mutual Funds, Commodities
Actual return on plan assets:
Defined Benefit Plan, Fair Value of Plan Assets	37,302	28,558
Real Asset Mutual Funds, Commodities \| Fair Value, Inputs, Level 3 [Member]
Actual return on plan assets:
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held	0	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Sold	0	(2,857)
Defined Benefit Plan Sales, Total	5,711
Defined Benefit Plan, Purchases, Total	0	(21,278)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	117	(3,776)
Defined Benefit Plan, Fair Value of Plan Assets	0	5,594	33,505
Fixed Income Mutual Funds, Insurance Contracts
Actual return on plan assets:
Defined Benefit Plan, Fair Value of Plan Assets	24,935	21,255
Fixed Income Mutual Funds, Insurance Contracts \| Fair Value, Inputs, Level 3 [Member]
Actual return on plan assets:
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held	21	25
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Sold	0	0
Defined Benefit Plan Sales, Total	98
Defined Benefit Plan, Purchases, Total	108	(38)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	183	(54)
Defined Benefit Plan, Fair Value of Plan Assets	$ 1,514	$ 1,300	$ 1,367

Purchases of plan assets that occurred during the period.

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- Definition

Sale of plan assets that occurred during the period.

+ References

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- References

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

Reference 1: 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=82843861&loc=d3e1928-114920

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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