Employee Benefit Plans (Pension And Other Postretirement Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Successor | Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2,991		$ 5,982
Expected return on plan assets	(4,499)		(8,996)
Pension settlement	(487)		(487)
Amortization of other actuarial losses (gains)	0		0
Net benefit cost (credit)	(1,995)		(3,501)
Successor | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	171		341
Interest cost	1,059		2,117
Curtailments	0		0
Amortization of prior service credits	0		0
Amortization of other actuarial losses (gains)	0		0
Net benefit cost (credit)	$ 1,230		$ 2,458
Predecessor | Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 3,197		$ 6,535
Expected return on plan assets		(4,444)		(8,982)
Pension settlement		454		454
Amortization of other actuarial losses (gains)		924		1,681
Net benefit cost (credit)		131		(312)
Predecessor | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost		105		265
Interest cost		1,138		2,272
Curtailments		(970)		(970)
Amortization of prior service credits		(2,672)		(5,345)
Amortization of other actuarial losses (gains)		(566)		(1,132)
Net benefit cost (credit)		$ (2,965)		$ (4,910)