Fair Value Measurements Narrative (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jun. 08, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of investment in Ferrous Resources prior to acquisition of controlling interest				$ 36	$ 0
Fair Value Of Property Plant And Equipment Impaired During Period		$ 17	$ 11	17	11
Impairment of Long-Lived Assets Held-for-use		6	4	10	6
Carrying value of property plant and equipment impaired during period		27	17	27	17
Other Segments and Holding Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized and unrealized losses				(28)	(97)
Investment Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				(12)	(33)
Fair Value, Measurements, Recurring [Member] | Other Segments and Holding Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized and unrealized losses				(28)	(97)
Distribution-in-kind				0	110
Purchases, additions and settlements, net				102	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		182	153	182	153	$ 154	$ 138
Fair Value, Measurements, Recurring [Member] | Investment Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized and unrealized losses				(12)	(100)
Distribution-in-kind				0	(110)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		63	$ 75	63	75	$ 75	$ 287
Fair Value, Measurements, Recurring [Member] | Holding Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Distribution-in-kind					$ 110
Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring [Member] | Holding Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, additions and settlements, net				100
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 100		$ 100
Ferrous Resources [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of investment in Ferrous Resources prior to acquisition of controlling interest	$ 36