Employee Benefit Plans Employee Benefit Plans 1 (Details)	12 Months Ended
	Dec. 31, 2016 participant	Dec. 31, 2015 item
Pension Plan
Employee benefit plans
Minimum age for eligibility under the Pension Plan | item		21
Minimum period of service for eligibility under the Pension Plan	5 years
Normal retirement benefit (as a percent)	2.00%
Number of highest consecutive years' average earnings used in computing retirement benefit	5 years
Maximum number of years of credited service considered in determining retirement benefit	40 years
Number of participants in the Pension Plan | participant	957
Pension Plan
Employee benefit plans
Percentage of participant's eligible pay contributed to the plan by the employer	5.25%
Eligibility for employer matching contributions, period of service	3 years