Employee Benefit Obligations - General (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) plan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2016 item
Employee Benefit Obligations
Underfunded defined benefit pension liabilities	$ 963.0	$ 707.0
Less current portion	(25.0)	(19.0)
Long-term defined benefit pension liabilities	938.0	688.0
Retiree medical and other postemployment benefits	226.0	148.0
Deferred compensation plans	272.0	281.0
Other	61.0	30.0
Employee benefit obligations	1,497.0	1,147.0
Total net periodic benefit cost	169.0	96.0	$ 132.0
Amounts recognized in the consolidated balance sheets
Long-term pension asset	147.0	2.0
Defined Benefit Pension Plans
Amounts recognized in the consolidated balance sheets
Long-term pension asset	147.0	2.0
Defined benefit pension liabilities	(963.0)	(707.0)
Net amount recognized	(816.0)	(705.0)
Multiemployer Plans
Employee Benefit Obligations
Total net periodic benefit cost		$ 2.0
Imposition of nondeductible excise tax, if a multiemployer defined benefit pension plan fails to satisfy certain minimum funding requirements (as a percent)		5.00%
U.S.
Employee Benefit Obligations
Total net periodic benefit cost	81.0	$ 74.0	102.0
Amounts recognized in the consolidated balance sheets
Defined benefit pension liabilities	(679.0)	(374.0)
Net amount recognized	(679.0)	(374.0)
U.S. | Rexam
Amounts recognized in the consolidated balance sheets
Annuitized Unfunded Obligation	33.0
U.S. | Rexam | Other long term assets
Amounts recognized in the consolidated balance sheets
Annuitized Unfunded Corresponding Asset	33.0
Foreign Plans
Employee Benefit Obligations
Total net periodic benefit cost	88.0	22.0	$ 30.0
Amounts recognized in the consolidated balance sheets
Long-term pension asset	147.0	2.0
Defined benefit pension liabilities	(284.0)	(333.0)
Net amount recognized	$ (137.0)	$ (331.0)
Rexam Pension Plan | Rexam
Employee Benefit Obligations
Number of defined benefit plans acquired | item				11
Rexam Retiree Medical Plan | Rexam
Employee Benefit Obligations
Number of defined benefit plans acquired | item				2
Multi-employer defined benefit plan
Employee Benefit Obligations
Number of defined benefit plans acquired | plan	3