Accumulated Other Comprehensive Income (Loss) - AOCI (Details) - USD ($) $ in Millions	3 Months Ended
Jun. 30, 2017	Apr. 01, 2017
Predecessor
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 0.0	$ 181.5
Reclassification from other comprehensive income to earnings		23.0
Current period change		5.5
Fresh start reporting adjustment		448.5
Ending Balance		0.0
Predecessor \| Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0.0	(148.2)
Reclassification from other comprehensive income to earnings		0.0
Current period change		5.5
Fresh start reporting adjustment		142.7
Ending Balance		0.0
Predecessor \| Net Actuarial Loss Associated with Postretirement Plans and Workers’ Compensation Obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0.0	(256.3)
Reclassification from other comprehensive income to earnings		5.8
Current period change		0.0
Fresh start reporting adjustment		250.5
Ending Balance		0.0
Predecessor \| Prior Service Cost Associated with Postretirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0.0	21.7
Reclassification from other comprehensive income to earnings		(1.4)
Current period change		0.0
Fresh start reporting adjustment		(20.3)
Ending Balance		0.0
Predecessor \| Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0.0	(94.2)
Reclassification from other comprehensive income to earnings		18.6
Current period change		0.0
Fresh start reporting adjustment		75.6
Ending Balance		0.0
Predecessor \| Total Accumulated Other Comprehensive (Loss) Income
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0.0	(477.0)
Ending Balance		$ 0.0
Successor
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Current period change	0.5
Ending Balance	3,231.7
Successor \| Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Current period change	0.5
Ending Balance	0.5
Successor \| Net Actuarial Loss Associated with Postretirement Plans and Workers’ Compensation Obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Current period change	0.0
Ending Balance	0.0
Successor \| Prior Service Cost Associated with Postretirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Current period change	0.0
Ending Balance	0.0
Successor \| Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Current period change	0.0
Ending Balance	0.0
Successor \| Total Accumulated Other Comprehensive (Loss) Income
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance	$ 0.5

Other Comprehensive Income (Loss), Fresh Start Reporting Adjustments

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- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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-Name Accounting Standards Codification
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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
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-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686

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