Qualified Employee Benefit Plans - Actuarial Computations Used to Determine Net Periodic Costs (Details) - Retirement Plan [Member]	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assumptions used to determine net periodic benefit costs [Abstract]
Discount rate on benefit obligations	4.75%	4.30%	5.30%
Expected long-term rate of return on plan assets	6.50%	7.00%	7.50%

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Expected Long-Term Rate of Return on Plan Assets
-URI http://asc.fasb.org/extlink&oid=6512046

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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