Debt - Recourse Debt (Details) - USD ($) $ in Millions	1 Months Ended				3 Months Ended		6 Months Ended
	May 31, 2016	Jan. 31, 2016	Apr. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	May 16, 2016	Jan. 01, 2016	Apr. 02, 2015
Debt Instrument [Line Items]
Redeemed notes		$ 125
Gain (loss) on extinguishment of debt					$ 0	$ (117)	$ 4	$ (141)
Senior Unsecured Note LIBOR plus 3% due 2019 [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt	$ (4)
8% senior unsecured notes due 2017 and 2020 [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt						$ 82		82
Senior Notes [Member] | 6.00% senior notes due 2026 [Domain]
Debt Instrument [Line Items]
Interest rate on senior notes									6.00%
Issued senior notes									$ 500
Senior Notes [Member] | Senior Unsecured Note LIBOR plus 3% due 2019 [Member]
Debt Instrument [Line Items]
Redeemed notes	$ 495
Senior Notes [Member] | 8.0% Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Interest rate on senior notes											8.00%
Senior Notes [Member] | 5.50% Percent Senior Notes Due 2025 [Domain]
Debt Instrument [Line Items]
Interest rate on senior notes											5.50%
Issued senior notes											$ 575
Senior Notes [Member] | 8.0% Senior Notes Due 2020 [Domain]
Debt Instrument [Line Items]
Interest rate on senior notes											8.00%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt								$ (23)
Unsecured Debt [Member] | 7.375% Senior Notes Due 2021 [Member] [Member]
Debt Instrument [Line Items]
Interest rate on senior notes										7.375%
Unsecured Debt [Member] | 4.875% Senior Notes Due 2023 [Member] [Member]
Debt Instrument [Line Items]
Interest rate on senior notes										4.875%
Unsecured Debt [Member] | 5.5% Senior Notes Due 2024 [Member] [Member]
Debt Instrument [Line Items]
Interest rate on senior notes										5.50%
Unsecured Debt [Member] | 5.5% Senior Notes Due 2025 [Member] [Member]
Debt Instrument [Line Items]
Interest rate on senior notes										5.50%
Unsecured Debt [Member] | 7.75% Senior Notes Due 2015 [Member]
Debt Instrument [Line Items]
Redeemed notes				$ 151
Interest rate on senior notes				7.75%
Unsecured Debt [Member] | 9.75% Senior Notes Due 2016 [Member] [Domain]
Debt Instrument [Line Items]
Redeemed notes				$ 164
Interest rate on senior notes				9.75%
Unsecured Debt [Member] | 8.0% Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Redeemed notes			$ 344
Unsecured Debt [Member] | 8.0% Senior Notes Due 2020 [Domain]
Debt Instrument [Line Items]
Redeemed notes			$ 156
Parent Company [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt							$ 7