Employment Benefit Plans Postretirement Health Care and Other Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unfunded Accumulated Postretirement Benefit Obligations Determined By Company	$ 7,820
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	182
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	11
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	258
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	$ 17
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.50%	4.00%
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 282
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	311
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	327
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	353
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	387
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	2,452
Defined Benefit Plan, Benefit Obligation	$ 4,112
Maximum [Member]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	5.60%
Minimum [Member]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	4.50%
Successor [Member]
Postemployment Benefits, Period Expense	$ 4,164	$ 8,846	$ 2,570