Debt (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Deferred financing fees	$ 12		$ 12			$ 6
Loss on extinguishment of debt	22	$ 2	22	$ 4
Fair value of debt	1,125		1,125			1,129
Accrued interest	13		13			$ 31
Credit facility
Debt Instrument [Line Items]
Loss on extinguishment of debt	(1)		(1)
Maximum borrowing limit	220		220		$ 180
Borrowing available under credit facility	189		189
Outstanding lines of credit	$ 0		$ 0
Interest rate at period end for line of credit facility	2.30%		2.30%
Amount of letters of credit outstanding	$ 31		$ 31
CGC Credit Facility CAD
Debt Instrument [Line Items]
Interest rate at period end for line of credit facility	2.07%		2.07%
4.875% senior notes due 2027
Debt Instrument [Line Items]
Face amount of debt	$ 500		$ 500
Debt instrument interest rate	4.875%		4.875%
Deferred financing fees	$ 7		$ 7
Redemption price percentage			102.438%
Amount of premium associated with contractual redemption upon change in control			101.00%
7.75% senior notes due 2018
Debt Instrument [Line Items]
Debt instrument interest rate						7.75%
Amount paid in consideration of debt repurchase	$ 536		$ 536
Premiums paid on repurchased debt	20		20
Accrued interest paid on repurchased debt	16		16
Loss on extinguishment of debt	$ (21)		$ (21)
6.3% senior notes due 2016
Debt Instrument [Line Items]
Debt instrument interest rate	6.30%		6.30%
Amount paid in consideration of debt repurchase	$ 144		$ 144
Premiums paid on repurchased debt	4		4
Accrued interest paid on repurchased debt	3		3
Loss on extinguishment of debt		$ 2		$ 4
Repurchase of outstanding debt	$ 137		$ 137