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, 2018	$ 9,906	$ 484	$ 5	$ 13,793	$ (3,433)	$ (943)
Balance, Common Stock, shares at Dec. 31, 2018			536.3
Net income (loss)	265				265
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	400					400
APIC, Share-based Payment Arrangement, Recognition and Exercise	2			2
Proceeds from Issuance of Preferred Stock and Preference Stock	227
Stock Issued During Period, Shares, New Issues			0.0
Stock Issued During Period, Value, New Issues			$ 0	0
Preferred dividends declared	(10)				(10)
Common dividends declared	(289)				(289)
Balance, value at Mar. 31, 2019	10,501	711	$ 5	13,795	(3,467)	(543)
Balance, Common Stock, shares at Mar. 31, 2019			536.3
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
Net income (loss)	$ (2,421)				(2,421)
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	$ 464					464
Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture	0.1
APIC, Share-based Payment Arrangement, Recognition and Exercise	$ 3			3
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 557
Stock Issued During Period, Shares, New Issues	26.7		26.7
Stock Issued During Period, Value, New Issues	$ 439			438
Preferred dividends declared	(21)				(21)
Common dividends declared	(264)				(264)
Balance, value at Mar. 31, 2020	$ 9,798	$ 1,489	$ 6	$ 14,334	$ (6,592)	$ 561
Balance, Common Stock, shares at Mar. 31, 2020	567.7		567.7