Investment Securities (Available-for-sale and Held-to-maturity Securities, Unrealized Losses) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Purchase of investment securities available-for-sale			$ 300,000,000	$ 68,000,000
Transfer of HTM securities	$ 0	$ 0	0	0
Purchase of investment securities HTM	0	0	0	15,000,000
Proceeds from sale of held-to-maturity securities		0	0	0
Available-for-sale Securities Pledged as Collateral	1,400,000,000		1,400,000,000		$ 879,000,000
Agency - Commercial
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 4,000,000		$ 4,000,000		$ 0
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Positions | security	1		1		0
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months or Over, Unrealized Loss	$ 0		$ 0		$ 0
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 429,000,000		$ 429,000,000		$ 528,000,000
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Positions | security	27		27		34
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ (5,000,000)		$ (5,000,000)		$ (6,000,000)
Agency - Residential
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 0		$ 0		$ 0
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Positions | security	0		0		0
Held-to-maturity Securities, Unrealized Loss Position with Duration 12 Months or Over, Unrealized Loss	$ 0		$ 0		$ 0
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 356,000,000		$ 356,000,000		$ 385,000,000
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Positions | security	44		44		43
Held-to-maturity Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ (3,000,000)		$ (3,000,000)		$ (4,000,000)
US Government-sponsored Enterprises Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Purchase of investment securities available-for-sale	77,000,000	40,000,000	300,000,000	68,000,000
Sales of AFS securities	62,000,000	175,000,000	62,000,000	175,000,000
Gain on sales of AFS securities	1,000,000	$ 1,000,000	1,000,000	$ 1,000,000
Agency - Commercial
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 5,000,000		$ 5,000,000		$ 6,000,000
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Securities | security	1		1		1
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Unrealized Loss	$ 0		$ 0		$ 0
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 367,000,000		$ 367,000,000		$ 345,000,000
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Securities | security	30		30		29
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ (5,000,000)		$ (5,000,000)		$ (5,000,000)
Agency - Residential
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 0		$ 0		$ 0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Securities | security	0		0		0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Unrealized Loss	$ 0		$ 0		$ 0
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 611,000,000		$ 611,000,000		$ 748,000,000
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Securities | security	49		49		55
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ (12,000,000)		$ (12,000,000)		$ (16,000,000)
Municipal obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 0		$ 0		$ 0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Securities | security	0		0		0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Unrealized Loss	$ 0		$ 0		$ 0
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 20,000,000		$ 20,000,000		$ 17,000,000
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Securities | security	7		7		8
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ 0		$ 0		$ 0
Corporate debt obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Fair Value	$ 0		$ 0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Number of Securities | security	0		0
Available-for-sale Securities, Unrealized Loss Position with Duration 12 Months and Over, Unrealized Loss	$ 0		$ 0
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Fair Value	$ 0		$ 0
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Number of Securities | security	1		1
Available-for-Sale Securities, Unrealized Loss Position with Duration Under 12 Months, Unrealized Loss	$ 0		$ 0