Employee Benefit Plans, Projected Benefit Obligation, Accumulated Benefit Obligation and Fair Value of Plan Assets (Details) - Defined Benefit Pension Plans Combined [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Projected Benefit Obligation and Fair Value of Plan Assets [Abstract]
Projected benefit obligation	$ 40,754	$ 39,469	$ 40,884
Fair value of plan assets	35,467	31,835	30,575
Accumulated Benefit Obligation and Fair Value of Plan Assets [Abstract]
Accumulated benefit obligation	37,822	36,302
Fair value of plan assets	$ 35,467	$ 31,835	$ 30,575

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Projected Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6522206

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Postretirement Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503904

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