CONSOLIDATED STATEMENTS OF SHAREHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common shares [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained earnings [Member]
Beginning balance at Dec. 31, 2018	$ 3,572	$ 3	$ 2,466	$ 1,058	$ 45
Beginning balance (Premium Amortization on Purchased Callable Debt Securities Guidance [Member]) at Dec. 31, 2018						$ (2)	$ (2)
Comprehensive income:
Net Income	586			586
Other comprehensive income (loss), net of tax	561				561
Total comprehensive income	1,147
Cash dividends to Ameriprise Financial, Inc.	(850)			(850)
Ending balance at Sep. 30, 2019	3,867	3	2,466	792	606
Beginning balance at Jun. 30, 2019	3,855	3	2,466	861	525
Comprehensive income:
Net Income	231			231
Other comprehensive income (loss), net of tax	81				81
Total comprehensive income	312
Cash dividends to Ameriprise Financial, Inc.	(300)			(300)
Ending balance at Sep. 30, 2019	3,867	3	2,466	792	606
Beginning balance at Dec. 31, 2019	3,336	3	2,466	293	574
Beginning balance (Current expected credit losses guidance [Member]) at Dec. 31, 2019						$ (7)	$ (7)
Comprehensive income:
Net Income	567			567
Other comprehensive income (loss), net of tax	219				219
Total comprehensive income	786
Cash dividends to Ameriprise Financial, Inc.	(650)			(650)
Ending balance at Sep. 30, 2020	3,465	3	2,466	203	793
Beginning balance at Jun. 30, 2020	3,961	3	2,466	787	705
Comprehensive income:
Net Income	(434)			(434)
Other comprehensive income (loss), net of tax	88				88
Total comprehensive income	(346)
Cash dividends to Ameriprise Financial, Inc.	(150)			(150)
Ending balance at Sep. 30, 2020	$ 3,465	$ 3	$ 2,466	$ 203	$ 793