Debt Revolver (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) extension	Mar. 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 10, 2015 USD ($)	May 31, 2015 USD ($)
Debt Instrument [Line Items]
Other Long-term Debt, Noncurrent	$ 7,309,000,000			$ 7,309,000,000	$ 2,000,000,000
Line of Credit Facility, Expiration Date	May 31, 2020
Ratio of Indebtedness to Net Capital	0.29
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 3,300,000,000	$ 3,000,000,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 0
Line of Credit Facility, Number of One Year Extensions | extension	2
Line of Credit, Period of Extension Options	1 year
Line of Credit Facility, Remaining Borrowing Capacity	$ 200,000,000
Bridge Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 100,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 500,000,000
Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						0.65