Consolidated Statement of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, value at Dec. 31, 2016	$ 7,356	$ 336	$ 3	$ 9,932	$ (2,518)	$ (397)
Balance, Common Stock, shares at Dec. 31, 2016			331.0
Net income (loss)	771				771
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	52					52
APIC, Share-based Payment Arrangement, Recognition and Exercise	4			4
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 315
Stock Redeemed or Called During Period, Shares	(167.0)
Preferred Stock, Redemption Amount	$ (173)
Issuance costs of redeemed preferred stock	$ (6)
Stock Issued During Period, Shares, New Issues	7.6		60.3
Stock Issued During Period, Value, New Issues	$ 1,238		$ 1	1,237
Payments for Repurchase of Common Stock	0
Preferred dividends declared	(32)				(32)
Common dividends declared	(777)				(777)
Balance, value at Dec. 31, 2017	8,754	484	$ 4	11,173	(2,562)	(345)
Balance, Common Stock, shares at Dec. 31, 2017			391.3
Net income (loss)	129				129
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	(598)					(598)
APIC, Share-based Payment Arrangement, Recognition and Exercise	10			10
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Issuance costs of redeemed preferred stock	$ 0
Stock Issued During Period, Shares, New Issues	20.8		145.0
Stock Issued During Period, Value, New Issues	$ 2,611		$ 1	2,610
Payments for Repurchase of Common Stock	0
Preferred dividends declared	(36)				(36)
Common dividends declared	(964)				(964)
Balance, value at Dec. 31, 2018	$ 9,906	484	$ 5	13,793	(3,433)	(943)
Balance, Common Stock, shares at Dec. 31, 2018	536.3		536.3
Net income (loss)	$ 688				688
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	$ 1,040					1,040
Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture	0.1
APIC, Share-based Payment Arrangement, Recognition and Exercise	$ 13			13
Stock Repurchased During Period, Shares	(6.9)		(6.9)
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 617
Stock Redeemed or Called During Period, Shares	(169.0)
Preferred Stock, Redemption Amount	$ (175)
Issuance costs of redeemed preferred stock	$ (6)
Stock Issued During Period, Shares, New Issues	11.4		11.4
Stock Issued During Period, Value, New Issues	$ 190			190
Repurchase of common stock	(103)			(103)
Payments for Repurchase of Common Stock	103
Preferred dividends declared	(54)				(54)
Common dividends declared	(1,081)				(1,081)
Balance, value at Dec. 31, 2019	$ 11,041	$ 932	$ 5	$ 13,893	$ (3,886)	$ 97
Balance, Common Stock, shares at Dec. 31, 2019	540.9		540.9