Investment Securities (Narrative) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Securities with no credit impairment in unrealized loss position		228
Investment securities available-for-sale, Amortized Cost	[1]	$ 10,829	$ 10,491
Investment securities available-for-sale, Fair Value	[1]	10,787	10,519
Investment securities held-to-maturity, Amortized Cost		1,582	1,981
Held-to-maturity securities, Fair Value		1,576
Carrying value of securities pledged		1,500
Liabilities secured by pledged collateral		$ 1,000
U.S. Treasury and other U.S. government agency securities
Securities with no credit impairment in unrealized loss position		7
Investment securities available-for-sale, Amortized Cost		$ 2,772	2,769
Investment securities available-for-sale, Fair Value		$ 2,779	2,763
Residential mortgage-backed securities
Securities with no credit impairment in unrealized loss position		179
Investment securities available-for-sale, Amortized Cost	[2]		7,513
Investment securities available-for-sale, Fair Value	[2]	$ 7,872	7,545
Investment securities held-to-maturity, Amortized Cost	[2],[3]		1,981
Held-to-maturity securities, Fair Value	[2],[3]	$ 1,576	1,973
Auction-rate state and municipal securities
Securities with no credit impairment in unrealized loss position		14
Auction-rate preferred securities
Securities with no credit impairment in unrealized loss position		28
Auction-rate securities
ARS portfolio redeemed or sold since acquisition		96.00%
ARS portfolio redeemed or sold since acquisition at or above cost		90.00%
Investment securities available-for-sale, Amortized Cost		$ 55	76
Investment securities available-for-sale, Fair Value		54	$ 77
Prepayment options | Residential mortgage-backed securities
Investment securities available-for-sale, Amortized Cost	[2]	7,900
Investment securities available-for-sale, Fair Value		7,900
Investment securities held-to-maturity, Amortized Cost	[2],[3]	1,600
Held-to-maturity securities, Fair Value		$ 1,600

[1] Included auction-rate securities at amortized cost and fair value of $55 million and $54 million, respectively, as of December 31, 2016 and $76 million and $77 million, respectively, as of December 31, 2015.

[2] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

[3] The amortized cost of investment securities held-to-maturity included net unrealized losses of $12 million at December 31, 2016 and $15 million at December 31, 2015 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss.