Benefit Obligations (Pension and Other Postretirement Obligations Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 27, 2014	Nov. 05, 2013
Defined Benefit Plan Disclosure [Line Items]
Pension and postretirement net periodic benefit cost		$ (54)	$ (52)	$ (113)
Multiemployer plans, funded status		At least 80 percent	At least 80 percent	At least 80 percent
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement gain (loss)		$ 0	$ 0	$ 78
Curtailment gain (loss)		0	3	0
Amortization of prior service cost (credit)		0	0	0
Lump-sum buyout payments		1	0
Pension Benefits [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Settlement gain (loss)				78
Lump-sum buyout payments	$ 143
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement gain (loss)		0	0	0
Curtailment gain (loss)		0	0	0
Amortization of prior service cost (credit)		(3)	0	(83)
Lump-sum buyout payments		0	$ 0
Postretirement Benefits [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)						$ (92)
Amortization of prior service cost (credit)				(84)
Lump-sum buyout payments				$ 40
Narrows Union Employees [Member] | Postretirement Benefits [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)					$ (5)
Change in Assumptions for Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and postretirement net periodic benefit cost		$ 29