Equity (Narrative) (Details) $ / shares in Units, TangibleEquityUnits in Millions, TEUPurchaseContracts in Millions		3 Months Ended	12 Months Ended
	Dec. 15, 2016 $ / shares	Dec. 31, 2016 USD ($) TangibleEquityUnits shares TEUPurchaseContracts $ / shares	Sep. 27, 2014 USD ($) TangibleEquityUnits $ / shares	Oct. 01, 2016 USD ($)
Class of Stock [Line Items]
TEU's issued (in units) | TangibleEquityUnits			30.0
TEU's Dividend Rate			4.75%
Proceeds from Issuance of Tangible Equity Units, Net | $			$ 1,454,000,000
TEUs, stated amount per unit (in dollars per unit) | $ / shares			$ 50
TEUs, Equity Component | $			$ 1,295,000,000
TEUs, Debt Component | $		$ 53,000,000	205,000,000	$ 71,000,000
Tangible Equity Units, Purchase Contracts, Settled | TEUPurchaseContracts		20.4
Tangible Equity Units, Outstanding | TangibleEquityUnits		9.6
Convertible Debt [Member] | Tangible Equity Unit, Senior Amortizing Note [Member]
Class of Stock [Line Items]
Senior amortizing note, initial principal amount | $			$ 6.83
Senior amortizing note, interest rate			1.50%
Senior amortizing note, quarterly principal and interest payment | $			$ 0.59
Class A [Member]
Class of Stock [Line Items]
Stock Issued During Period, Value, Conversion of Convertible Securities		21,700,000
Common Stock, Dividends, Per Share, Cash Paid | $ / shares	$ 0.225
Class A [Member] | Convertible Debt [Member] | Tangible Equity Unit, Senior Amortizing Note [Member]
Class of Stock [Line Items]
Senior amortizing note, conversion price | $ / shares		$ 46.79
Senior amortizing note, number of shares per contract if applicable market value equal to or greater than conversion price		1.0685
Senior amortizing note, reference price | $ / shares		$ 37.44
Senior amortizing note, if applicable market value greater than reference price, number of shares equal to amount divided by Applicable Market Value | $ / shares		$ 50
Senior amortizing note, number of shares per contract, if Applicable Market Value is less than or equal to reference price		1.3358
Senior amortizing note, consecutive trading days for calculation of applicable market value		20 days
Debt Instrument, Convertible, Dividend Threshold Amount | $ / shares		$ 0.075
Senior amortizing note, incremental common shares attributable to dilutive effect of conversion, if applicable market value higher than reference price		2,600,000
Class A [Member] | Convertible Debt [Member] | Tangible Equity Unit, Senior Amortizing Note [Member] | Minimum [Member]
Class of Stock [Line Items]
Senior amortizing note, number of shares to be issued		10,300,000
Class A [Member] | Convertible Debt [Member] | Tangible Equity Unit, Senior Amortizing Note [Member] | Maximum [Member]
Class of Stock [Line Items]
Senior amortizing note, number of shares to be issued		12,900,000
Class A [Member] | Share Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		31,700,000