Employee Benefit Plans and Other Postretirement Plans - Change in Benefit Obligations and Change in Fair Value of Plan Assets Related to Pension and Postretirement Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at plan year end	$ 805,900,000		$ 772,100,000
Amounts Recognized on Consolidated Balance Sheets
Noncurrent liabilities	(361,700,000)		(193,500,000)
Amounts Recognized in Accumulated Other Comprehensive (Income) Loss (Pre-Tax)
Accumulated benefit obligation for plans with obligations in excess of plan assets	1,080,000,000
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Weighted-Average Assumptions Used to Determine Benefit Obligation, Discount Rate	4.14%		5.00%		4.25%
Change in Benefit Obligations [Roll Forward]
Benefit obligation at beginning of period	929,800,000		378,700,000
Service cost	22,700,000		24,500,000		22,400,000
Interest cost	45,900,000		21,500,000		14,800,000
Plan amendments	2,600,000		13,800,000	[1]
Actuarial (gain) loss	159,200,000	[2]	(53,500,000)	[2]
Acquisitions	0		554,000,000
Special termination benefits	300,000		0		0
Participant contributions	0		0
Benefits paid	(30,900,000)		(9,200,000)
Benefit obligation at plan year end	1,129,600,000		929,800,000		378,700,000
Accumulated benefit obligation portion of above	1,078,600,000		884,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value at beginning of period	772,100,000		238,400,000
Acquisitions	0		486,200,000
Actual return on plan assets	63,400,000		26,600,000
Company contributions	1,300,000		30,100,000
Participant contributions	0		0
Benefits paid	(30,900,000)		(9,200,000)
Fair value of plan assets at plan year end	805,900,000		772,100,000		238,400,000
Underfunded status	(323,700,000)		(157,700,000)
Amounts Recognized on Consolidated Balance Sheets
Current liabilities	(1,100,000)		(800,000)
Noncurrent liabilities	(322,600,000)		(156,900,000)
Accrued obligation recognized at December 31	(323,700,000)		(157,700,000)
Amounts Recognized in Accumulated Other Comprehensive (Income) Loss (Pre-Tax)
Amounts Recognized in Accumulated Other Comprehensive (Income) Loss (Pre-Tax)	27,600,000		31,600,000
Actuarial loss	172,600,000		26,700,000
Total	200,200,000		58,300,000
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Weighted-Average Assumptions Used to Determine Benefit Obligation, Discount Rate	3.95%		4.85%		4.00%
Change in Benefit Obligations [Roll Forward]
Benefit obligation at beginning of period	26,300,000		31,800,000
Service cost	1,600,000		2,100,000		1,900,000
Interest cost	1,200,000		1,300,000		1,200,000
Plan amendments	0		0
Actuarial (gain) loss	4,100,000	[2]	(7,800,000)	[2]
Acquisitions	0		200,000
Special termination benefits	0		0		0
Participant contributions	1,200,000		1,200,000
Benefits paid	(2,500,000)		(2,500,000)
Benefit obligation at plan year end	31,900,000		26,300,000		31,800,000
Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value at beginning of period	0		0
Acquisitions	0		0
Actual return on plan assets	0		0
Company contributions	1,300,000		1,300,000
Participant contributions	1,200,000		1,200,000
Benefits paid	(2,500,000)		(2,500,000)
Fair value of plan assets at plan year end	0		0		0
Underfunded status	(31,900,000)		(26,300,000)
Amounts Recognized on Consolidated Balance Sheets
Current liabilities	(1,400,000)		(1,200,000)
Noncurrent liabilities	(30,500,000)		(25,100,000)
Accrued obligation recognized at December 31	(31,900,000)		(26,300,000)
Amounts Recognized in Accumulated Other Comprehensive (Income) Loss (Pre-Tax)
Amounts Recognized in Accumulated Other Comprehensive (Income) Loss (Pre-Tax)	300,000		100,000
Actuarial loss	5,500,000		1,400,000
Total	$ 5,800,000		$ 1,500,000

[1] In 2013, the United Steel Workers (USW) ratified a master labor agreement with PCA under which certain USW-represented employees will have their pension accruals frozen under PCA's hourly pension plan, resulting in most of the $13.8 million increase in benefit obligations.

[2] The actuarial loss in 2014 is due primarily to a decrease in the weighted average discount rate and also our use of recently updated mortality assumptions from the Society of Actuaries which reflect longer expected participant longevity. In 2013, the discount rate increased resulting in an actuarial gain.