Employee Benefit Plans Unrecognized loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Gross of tax
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax			$ (1,452)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (22,017)	$ (17,722)	(37,341)
Recognized component of periodic pension cost			(944)
Unrecognized gains arising in current year	(931)	4,680	(13,168)
Ending Balance	(38,449)	(22,017)	(17,722)
Unrecognized Pension and Postretirement Plan Income (Cost)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(15,961)	(22,505)	(8,801)
Ending Balance	(15,675)	(15,961)	(22,505)
Pension Plans | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Gross of tax
AOCI before Tax, Attributable to Parent	30,396	38,082
Reclass adjustment for postretirement plan gain included in net income	(2,420)	(3,127)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	2,193	(4,559)
AOCI before Tax, Attributable to Parent	30,169	30,396	38,082
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	19,758	24,754
Recognized component of periodic pension cost	(1,573)	(2,033)
Unrecognized gains arising in current year	1,425	(2,963)
Ending Balance	19,610	19,758	24,754
Other Postretirement Benefit Plans | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost [Member]
Gross of tax
AOCI before Tax, Attributable to Parent	(5,334)	(3,123)
Reclass adjustment for postretirement plan gain included in net income	465	258
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		(2,469)
AOCI before Tax, Attributable to Parent	(4,869)	(5,334)	(3,123)
Other Postretirement Benefit Plans | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Gross of tax
AOCI before Tax, Attributable to Parent	(508)	(336)
Reclass adjustment for postretirement plan gain included in net income	86	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(761)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		(172)
AOCI before Tax, Attributable to Parent	(1,183)	(508)	(336)
Other Postretirement Benefit Plans | Unrecognized Pension and Postretirement Plan Income (Cost)
Gross of tax
AOCI before Tax, Attributable to Parent	(5,842)	(3,459)
Reclass adjustment for postretirement plan gain included in net income	551	258
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(761)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, before Tax		(2,641)
AOCI before Tax, Attributable to Parent	(6,052)	(5,842)	(3,459)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(3,798)	(2,249)
Recognized component of periodic pension cost	358
Unrecognized gains arising in current year	(495)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Prior to Curtailment, Net of Tax		168
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Prior to Curtailment, Net of Tax		(1,717)
Ending Balance	$ (3,935)	$ (3,798)	$ (2,249)