Subsequent Events (Details) - USD ($) $ in Millions	May 23, 2017	May 09, 2017	Feb. 02, 2017
Subsequent Event [Line Items]
Long-term debt, gross			$ 6,000
Senior Notes [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Long-term debt, gross	$ 1,700
Principal amount sublimit		$ 500
Accepted early debt tenders	$ 1,600
Senior Notes [Member] | Guaranteed Notes Due 2018 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Long-term debt, gross		$ 1,000
Debt instrument, interest rate, stated percentage	9.00%	9.00%
Principal amount sublimit	$ 1,200
Accepted early debt tenders	1,200
Senior Notes [Member] | Notes due 2017 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Long-term debt, gross	$ 112
Debt instrument, interest rate, stated percentage	8.375%	8.375%
Accepted early debt tenders	$ 388