Debt - Additional Information (Details) - USD ($)		Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Current portion of long-term debt		$ 46,000,000	$ 89,000,000
Long-term Debt, Gross		6,894,000,000
Secured Debt [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[1]	0
Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Current portion of long-term debt		20,000,000	21,000,000
CERP
Debt Instrument [Line Items]
Current portion of long-term debt		26,000,000	68,000,000
Long-term Debt, Gross		4,570,000,000
CGP | Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Current portion of long-term debt		20,000,000	$ 21,000,000
Long-term Debt, Gross		2,324,000,000
CGP | Variable Interest Entity, Primary Beneficiary [Member] | Secured Debt [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[1],[2]	$ 0

[1] See Note 17.

[2] Variable interest rate calculated as LIBOR plus 5.00%.