Condensed Consolidated Statements of Equity - USD ($) $ in Millions	Total	Preferred Stock	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Preferred Stock	Preferred Stock Additional paid-in capital	Common stock	Common stock Additional paid-in capital
Beginning Balance at Dec. 31, 2017	$ 9,176	$ 0	$ 0	$ 3,472	$ 4,255	$ 1,449
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	534				534
Other comprehensive income (loss)	(1,260)					(1,260)
Issuance of shares, net of expenses	1									$ 1
Stock-based compensation	19			19
Retirement or repurchase of shares	(5)			0	(5)
Ending Balance at Jun. 30, 2018	8,462	0	0	3,492	4,823	147
Beginning Balance at Mar. 31, 2018	8,687	0	0	3,485	4,568	634
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	257				257
Other comprehensive income (loss)	(487)					(487)
Stock-based compensation	7			7
Retirement or repurchase of shares	(2)			0	(2)
Ending Balance at Jun. 30, 2018	8,462	0	0	3,492	4,823	147
Beginning Balance at Dec. 31, 2018	8,276	0	0	3,462	5,286	(472)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,428				1,428
Other comprehensive income (loss)	2,232					2,232
Issuance of shares, net of expenses							$ 839	$ 839	$ 2	2
Stock-based compensation	15			15
Retirement or repurchase of shares	(427)			(174)	(253)
Ending Balance at Jun. 30, 2019	12,365	0	0	4,144	6,461	1,760
Beginning Balance at Mar. 31, 2019	10,117	0	0	3,448	5,963	706
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	720				720
Other comprehensive income (loss)	1,054					1,054
Issuance of shares, net of expenses							$ 839	$ 839	$ 1	$ 1
Stock-based compensation	10			10
Retirement or repurchase of shares	(376)			(154)	(222)
Ending Balance at Jun. 30, 2019	$ 12,365	$ 0	$ 0	$ 4,144	$ 6,461	$ 1,760