Debt - Recourse Debt (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Mar. 31, 2017	Jan. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 01, 2017	Jan. 01, 2016
Debt Instrument [Line Items]
Redeemed notes		$ 125
Gain (loss) on extinguishment of debt			$ 17	$ 4
7.375% Senior Notes Due 2021 [Member] [Member]
Debt Instrument [Line Items]
Redeemed notes	$ 276
8.0% Senior Notes Due 2020 [Domain]
Debt Instrument [Line Items]
Redeemed notes	$ 24
Unsecured Debt [Member] | 7.375% Senior Notes Due 2021 [Member] [Member]
Debt Instrument [Line Items]
Interest rate on senior notes					7.375%	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] | 8.0% Senior Notes Due 2020 [Domain]
Debt Instrument [Line Items]
Interest rate on senior notes					8.00%
Parent Company [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt			$ (47)	$ 7