Retirement benefits (Tables)

12 Months Ended

Dec. 31, 2018

Retirement Benefits [Abstract]

Summary of contribution expense

Our contribution expense was as follows:

	Successor				Predecessor
	Period from		Period from		Period from		Period from
	January 1, 2018		March 22, 2017		January 1, 2017		January 1, 2016
	through		through		through		through
	December 31, 2018		December 31, 2017		March 21, 2017		December 31, 2016
401(k) contribution expense	$	1,543	$	1,267	$	396	$	1,781