Financing Arrangements and Derivative Financial Instruments - $2.0 Billion Amended and Restated First Lien Revolving Credit Facility due 2021 (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Long-term debt, before deferred financing fees	$ 6,118,000,000	$ 5,235,000,000
Line of Credit | $2.0 Billion First Lien Revolving Credit Facility due 2021
Line of Credit Facility [Line Items]
Maximum borrowing capacity	2,000,000,000.0
Additional borrowing capacity which may be requested	250,000,000
Borrowing base amount below stated amount	266,000,000
Line of Credit | $2.0 Billion First Lien Revolving Credit Facility due 2021 | Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	800,000,000
Letters of credit outstanding	$ 37,000,000	40,000,000
Line of Credit | $2.0 Billion First Lien Revolving Credit Facility due 2021 | Letter of Credit | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.25%
Line of Credit | $2.0 Billion First Lien Revolving Credit Facility due 2021 | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,000,000,000.0
Annual commitment fee on undrawn amounts	0.30%
Maximum borrowing base increase based on value of certain cash	$ 200,000,000
Long-term debt, before deferred financing fees	$ 375,000,000	$ 85,000,000