Fair Value Measurements Narrative (Details) - USD ($) $ in Millions		6 Months Ended
	Jun. 08, 2015	Jun. 30, 2015	Jun. 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
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		(13)	(16)
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)		(13)	(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		(30)	(16)
Distribution-in-kind		0	110
Purchases, additions and settlements, net		102	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		190	234	$ 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		(13)	(65)
Distribution-in-kind		0	(110)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		62	110	$ 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
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