Employee Benefit Plans (Pension And Other Postretirement Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Successor | Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2,736		$ 8,718
Expected return on plan assets	(3,913)		(12,909)
Pension settlement	(229)		(716)
Amortization of other actuarial losses (gains)	0		0
Net benefit cost (credit)	(1,406)		(4,907)
Successor | Other postretirement benefits plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	170		511
Interest cost	1,058		3,175
Curtailments	(520)		(520)
Amortization of prior service credits	0		0
Amortization of other actuarial losses (gains)	0		0
Net benefit cost (credit)	$ 708		$ 3,166
Predecessor | Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 2,803		$ 9,338
Expected return on plan assets		(4,641)		(13,623)
Pension settlement		0		454
Amortization of other actuarial losses (gains)		2,292		3,973
Net benefit cost (credit)		454		142
Predecessor | Other postretirement benefits plan
Defined Benefit Plan Disclosure [Line Items]
Service cost		128		393
Interest cost		951		3,223
Curtailments		0		(970)
Amortization of prior service credits		(2,509)		(7,854)
Amortization of other actuarial losses (gains)		283		(849)
Net benefit cost (credit)		$ (1,147)		$ (6,057)