Retirement Plans (Narrative) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Contribution Plan Disclosure [Line Items]
Number of sponsored 401(k) plans \| item	2
Expense for matching and discretionary contributions	$ 5,060	$ 2,616	$ 2,686
Contributes to various multiemployer pension plans	$ 4,207	$ 4,699	$ 4,793
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plans collective-bargaining arrangement percentage of contributions	5.00%

Number of sponsored 401(k) plans

No definition available.

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

Percentage of contributions required of employer under collective bargaining arrangement to total contributions required under all collective bargaining arrangements for pension and other postretirement plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

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