Employee Benefit Plans - Narrative (Details) - USD ($)	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Expected amortization of gain/loss next fiscal year	$ 0		$ 0
Effect of one percentage point increase on accumulated postretirement benefit obligation			50,000
Effect of one percentage point decrease on accumulated postretirement benefit obligation			$ (46,000)
Other Postretirement Benefit Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Medical postretirement plans, qualifying retirement age range			62 years
Other Postretirement Benefit Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Medical postretirement plans, qualifying retirement age range			65 years
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Expected amortization of pension prior service cost and actuarial gain/loss next fiscal year			$ 0
Projected benefit obligation, pension plans with accumulated benefit obligations in excess of plan assets	5,414,000		5,414,000
Accumulated benefit obligation, pension plans with accumulated benefit obligations in excess of plan assets	5,414,000		5,414,000
Fair value of plan assets, pension plans with accumulated benefit obligations in excess of plan assets	$ 0		$ 0
Pension Plans, Defined Benefit | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target portfolio allocation (as a percent)			100.00%
Pension Plans, Defined Benefit | Corporate Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities allocation (as a percent)	80.00%		80.00%	87.00%
Pension Plans, Defined Benefit | US Treasury and Government
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities allocation (as a percent)	12.00%		12.00%	4.00%
Pension Plans, Defined Benefit | Agency Securities
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities allocation (as a percent)	3.00%		3.00%	2.00%
Pension Plans, Defined Benefit | Other fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities allocation (as a percent)	5.00%		5.00%	7.00%
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, allowable matching percentage based on terms of the plan (as a percent)			100.00%
Employer matching contribution (as a percent)			3.00%
Employer matching contribution, allowable matching percentage after initial match (as a percent)			50.00%
Employer matching contribution, after initial match (as a percent)			2.00%
Employer matching contribution, discretionary match			4.00%
Cliff vesting period			2 years
Amounts expensed	$ 749,000
One-time Termination Benefits
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation					$ 5,500,000
Revaluation of Liabilities | Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Pension and postretirement benefit obligations adjustment for fresh start accounting		$ (74,000)
Revaluation of Liabilities | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Pension and postretirement benefit obligations adjustment for fresh start accounting		4,348,000
Predecessor | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, pension plans with accumulated benefit obligations in excess of plan assets		5,449,000		$ 5,467,000
Accumulated benefit obligation, pension plans with accumulated benefit obligations in excess of plan assets		5,449,000		5,467,000
Fair value of plan assets, pension plans with accumulated benefit obligations in excess of plan assets		0		0
Predecessor | Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Amounts expensed		$ 1,244,000		2,725,000
Predecessor | One-time Termination Benefits
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation				3,527,000	5,500,000
Reduction to withdrawal obligation				$ (1,973,000)	$ 5,500,000