Schedule I - Condensed Financial Information of Parent (Senior Notes and Junior Subordinated Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 4,630	$ 4,671
Less: Current maturities	(5)	0
Recourse Debt Non Current	4,625	$ 4,671
Unamortized (discounts)/premiums & debt issuance (costs)
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ (40)
Recourse Debt | Term Convertible Trust Securities 675 Due 2029 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest Rate	6.75%	6.75%
Recourse Debt Total	$ 0	$ 517
Recourse Debt | 8.00% Senior Unsecured Note Due 2017
Condensed Financial Statements, Captions [Line Items]
Interest Rate		8.00%
Recourse Debt | 8.00% Senior Unsecured Note Due 2020
Condensed Financial Statements, Captions [Line Items]
Interest Rate	8.00%	8.00%
Recourse Debt | 7.38% Senior Unsecured Note Due 2021
Condensed Financial Statements, Captions [Line Items]
Interest Rate		7.38%
Recourse Debt | 5.50% Senior Unsecured Note Due 2024
Condensed Financial Statements, Captions [Line Items]
Interest Rate		5.50%
Recourse Debt | 5.50% Unsecured senior notes due 2025 [Domain]
Condensed Financial Statements, Captions [Line Items]
Interest Rate		5.50%
Recourse Debt | 6.00% senior notes due 2026 [Domain]
Condensed Financial Statements, Captions [Line Items]
Interest Rate		6.00%
Recourse Debt | LIBOR | Senior Secured Term Loan due 2022 [Member]
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate	2.00%	2.00%
Recourse Debt | LIBOR | Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate	2.00%	2.00%
Recourse Debt | LIBOR | Senior Unsecured Note LIBOR plus 3% due 2019
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate	3.00%	3.00%
Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 4,630
Junior subordinated notes and debentures payable	0	$ 517
Parent Company | Unamortized (discounts)/premiums & debt issuance (costs)
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	(40)	(45)
Parent Company | Recourse Debt | Senior Secured Term Loan due 2022 [Member]
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 521	0
Parent Company | Recourse Debt | 4.875% Senior Notes Due 2023 [Member] [Member]
Condensed Financial Statements, Captions [Line Items]
Interest Rate	4.88%
Recourse Debt Total	$ 713	713
Parent Company | Recourse Debt | Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 207	$ 0
Parent Company | Recourse Debt | 8.00% Senior Unsecured Note Due 2017
Condensed Financial Statements, Captions [Line Items]
Interest Rate		8.00%
Parent Company | Recourse Debt | 8.00% Senior Unsecured Note Due 2020
Condensed Financial Statements, Captions [Line Items]
Interest Rate		8.00%
Parent Company | Recourse Debt | 7.38% Senior Unsecured Note Due 2021
Condensed Financial Statements, Captions [Line Items]
Interest Rate		7.38%
Parent Company | Recourse Debt | 5.50% Senior Unsecured Note Due 2024
Condensed Financial Statements, Captions [Line Items]
Interest Rate	5.50%	5.50%
Recourse Debt Total	$ 738	$ 738
Parent Company | Recourse Debt | 5.50% Unsecured senior notes due 2025 [Domain]
Condensed Financial Statements, Captions [Line Items]
Interest Rate	5.50%	5.50%
Recourse Debt Total	$ 573	$ 573
Parent Company | Recourse Debt | 6.00% senior notes due 2026 [Domain]
Condensed Financial Statements, Captions [Line Items]
Interest Rate	6.00%	6.00%
Recourse Debt Total	$ 500	$ 500
Parent Company | Recourse Debt | LIBOR | Senior Unsecured Note LIBOR plus 3% due 2019
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 0	$ 240
Basis spread on variable rate	3.00%	3.00%
Parent Company | Recourse Debt | LIBOR | 8.00% Senior Unsecured Note Due 2020
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 228	$ 469
Parent Company | Recourse Debt Excluding Junior Subordinated Debt
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	4,630	4,154
Recourse Debt Non Current	4,625	$ 4,154
Debt Maturity Year One [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	5
Debt Maturity Year Two [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	5
Debt Maturity Year Three [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	234
Debt Maturity Year Four [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	902
Debt Maturity Year Five [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	500
Debt Maturity Thereafter [Member] | Parent Company
Condensed Financial Statements, Captions [Line Items]
Recourse Debt Total	$ 3,024