Balance Sheet Accounts - Schedule of Changes in Accumulated Other Comprehensive Loss by Components, Net of Income Taxes (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2015	Mar. 31, 2016	Feb. 28, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (341.7)	$ (347.0)
Actuarial losses, net of $4.6 million of income taxes	(8.6)	0.0	$ 0.0
Amortization of actuarial losses and prior service credits, net of $1.7 million of income taxes	3.3	9.1	12.1
Amortization of actuarial losses and prior service credits, net of $5.8 million of income taxes		9.1
Ending balance	(347.0)	(337.9)	$ (321.4)
Amortization of actuarial losses and prior service credits, tax	1.7	5.8
Actuarial Losses, Net [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(342.6)	(347.8)
Actuarial losses, net of $4.6 million of income taxes	(8.6)
Amortization of actuarial losses and prior service credits, net of $1.7 million of income taxes	3.4
Amortization of actuarial losses and prior service credits, net of $5.8 million of income taxes		9.3
Ending balance	(347.8)	(338.5)
Actuarial losses, tax	4.6
Prior Service Credits, Net [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0.9	0.8
Actuarial losses, net of $4.6 million of income taxes	0.0
Amortization of actuarial losses and prior service credits, net of $1.7 million of income taxes	(0.1)
Amortization of actuarial losses and prior service credits, net of $5.8 million of income taxes		(0.2)
Ending balance	$ 0.8	$ 0.6