Employee Benefit Plans Unrecognized loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (59,063)	$ (32,974)	$ (38,449)
Unrecognized gains arising in current year	(937)	1,400	(609)
Ending Balance	(137)	(59,063)	(32,974)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(15,089)	(14,923)	(15,675)
Ending Balance	(15,001)	(15,089)	(14,923)
Pension Plans | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Before tax
AOCI before Tax, Attributable to Parent	24,347	28,559
Reclass adjustment for postretirement plan gain included in net income	(1,981)	(2,429)
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Before Tax		0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	1,180	(1,783)
AOCI before Tax, Attributable to Parent	23,546	24,347	28,559
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	18,961	18,564
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Net Of Tax		3,678
Recognized component of periodic pension cost	(1,543)	(1,892)
Unrecognized gains arising in current year	919	(1,389)
Ending Balance	18,337	18,961	18,564
Other Postretirement Benefit Plans | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost [Member]
Before tax
AOCI before Tax, Attributable to Parent	(3,940)	(4,404)
Reclass adjustment for postretirement plan gain included in net income	464	464
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		0
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Before Tax		0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	0
AOCI before Tax, Attributable to Parent	(3,476)	(3,940)	(4,404)
Other Postretirement Benefit Plans | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Before tax
AOCI before Tax, Attributable to Parent	(1,096)	(1,159)
Reclass adjustment for postretirement plan gain included in net income	92	95
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		(32)
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Before Tax		0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	56
AOCI before Tax, Attributable to Parent	(948)	(1,096)	(1,159)
Other Postretirement Benefit Plans | Total
Before tax
AOCI before Tax, Attributable to Parent	(5,036)	(5,563)
Reclass adjustment for postretirement plan gain included in net income	556	559
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		(32)
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Before Tax		0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	56
AOCI before Tax, Attributable to Parent	(4,424)	(5,036)	(5,563)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(3,928)	(3,617)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Prior to Curtailment, Net of Tax		435
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, Net of Tax		(25)
Tax Cuts and Jobs Act, Measurement Period Adjustment, Change in Tax Rate, Net Of Tax		(721)
Recognized component of periodic pension cost	433
Unrecognized gains arising in current year	44
Ending Balance	$ (3,451)	$ (3,928)	$ (3,617)