Investments (Contractual Maturities Debt Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Amortized cost
Total debt investment securities	$ 20,473	$ 15,417
Due in one year or less	102
Due after one year through five years	1,455
Due after five years through ten years	1,762
Due after ten years	$ 17,154
Average yield
Total debt investment securities	1.66%
Due in one year or less	1.99%
Due after one year through five years	1.88%
Due after five years through ten years	1.88%
Due after ten years	1.62%
Amortized cost
Total HTM and AFS investment securities	$ 20,932	$ 16,053
Due in one year or less	142
Due after one year through five years	1,594
Due after five years through ten years	1,932
Due after ten years	$ 17,264
Average yield
Total debt investment securities	1.69%
Due in one year or less	2.42%
Due after one year through five years	2.03%
Due after five years through ten years	1.96%
Due after ten years	1.63%
Municipal securities
Amortized cost
Total debt investment securities	$ 459
Due in one year or less	40
Due after one year through five years	139
Due after five years through ten years	170
Due after ten years	$ 110
Average yield
Total debt investment securities	3.23%
Due in one year or less	3.52%
Due after one year through five years	3.54%
Due after five years through ten years	2.84%
Due after ten years	3.33%
Amortized cost
Total debt investment securities	$ 1,513
Due in one year or less	102
Due after one year through five years	658
Due after five years through ten years	494
Due after ten years	$ 259
Average yield
Total debt investment securities	2.34%
Due in one year or less	1.99%
Due after one year through five years	2.51%
Due after five years through ten years	2.17%
Due after ten years	2.38%
U.S. Treasury securities
Amortized cost
Total debt investment securities	$ 155
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	$ 155
Average yield
Total debt investment securities	1.28%
Due in one year or less	0.00%
Due after one year through five years	0.00%
Due after five years through ten years	0.00%
Due after ten years	1.28%
Agency securities
Amortized cost
Total debt investment securities	$ 874
Due in one year or less	0
Due after one year through five years	351
Due after five years through ten years	274
Due after ten years	$ 249
Average yield
Total debt investment securities	2.07%
Due in one year or less	0.00%
Due after one year through five years	1.36%
Due after five years through ten years	2.43%
Due after ten years	2.66%
Agency guaranteed mortgage-backed securities
Amortized cost
Total debt investment securities	$ 16,841
Due in one year or less	0
Due after one year through five years	396
Due after five years through ten years	807
Due after ten years	$ 15,638
Average yield
Total debt investment securities	1.60%
Due in one year or less	0.00%
Due after one year through five years	1.37%
Due after five years through ten years	1.56%
Due after ten years	1.60%
Small Business Administration loan-backed securities
Amortized cost
Total debt investment securities	$ 1,015
Due in one year or less	0
Due after one year through five years	50
Due after five years through ten years	127
Due after ten years	$ 838
Average yield
Total debt investment securities	1.36%
Due in one year or less	0.00%
Due after one year through five years	1.38%
Due after five years through ten years	1.56%
Due after ten years	1.33%
Other debt securities
Amortized cost
Total debt investment securities	$ 75
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	60
Due after ten years	$ 15
Average yield
Total debt investment securities	2.16%
Due in one year or less	0.00%
Due after one year through five years	0.00%
Due after five years through ten years	1.99%
Due after ten years	2.85%