CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Net income (loss)	$ (42.3)us-gaap_NetIncomeLoss	$ 340.1us-gaap_NetIncomeLoss	$ (158.9)us-gaap_NetIncomeLoss
Income tax expense related to items of other comprehensive income	(2.4)us-gaap_OtherComprehensiveIncomeLossTax		(75.0)us-gaap_OtherComprehensiveIncomeLossTax
Other comprehensive income (loss), net of tax	4.4
Predecessor [Member]
Net income (loss)		340.1	(158.9)
Prior service credit arising during the period			27.8
Curtailment (gain) recognized in net income		(2.2)
Amortization of actuarial (gains) losses, net		0.9	55.3
Amortization of prior service costs (credits)		(0.3)	(24.1)
Gain arising during the period			187.8
Other comprehensive income (loss), before tax		(1.6)	246.8
Income tax expense related to items of other comprehensive income			(75.0)
Other comprehensive income (loss), net of tax		(1.6)	171.8
Elimination of Predecessor Company accumulated other comprehensive loss		121.7
Comprehensive income (loss)		460.2	12.9
Successor [Member]
Net income (loss)	(42.3)
Prior service credit arising during the period	6.8
Other comprehensive income (loss), before tax	6.8
Income tax expense related to items of other comprehensive income	(2.4)
Other comprehensive income (loss), net of tax	4.4
Comprehensive income (loss)	$ (37.9)

Elimination of Predecessor Company accumulated other comprehensive loss

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The amount of net gain (loss) recognized in net periodic benefit cost as a result of an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount before tax of cost (credit) of benefit changes attributable to plan participants' prior service resulting from a plan amendment or plan initiation that has not been recognized in net periodic benefit cost (credit).

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Amount before tax of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) related to pension and other postretirement benefit plans.

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

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Amount before tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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