Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	$ (35.0)	$ (216.0)
Unrealized loss position less than 12 months - fair value	4,563.0	25,715.0
Unrealized loss position 12 months or more - unrealized loss	(155.0)	(147.0)
Unrealized loss position 12 months or more - fair value	7,710.0	4,425.0
Total unrealized loss	(190.0)	(363.0)
Total fair value	12,273.0	30,140.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(35.0)	(216.0)
Unrealized loss position less than 12 months - fair value	4,563.0	25,669.0
Unrealized loss position 12 months or more - unrealized loss	(155.0)	(146.0)
Unrealized loss position 12 months or more - fair value	7,695.0	4,410.0
Total unrealized loss	(190.0)	(362.0)
Total fair value	12,258.0	30,079.0
US Treasury and Government Agencies Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(6.0)	(40.0)
Unrealized loss position less than 12 months - fair value	1,030.0	5,885.0
Unrealized loss position 12 months or more - unrealized loss	(13.0)	(2.0)
Unrealized loss position 12 months or more - fair value	2,445.0	120.0
Total unrealized loss	(19.0)	(42.0)
Total fair value	3,475.0	6,005.0
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(3.0)	(103.0)
Unrealized loss position less than 12 months - fair value	662.0	11,799.0
Unrealized loss position 12 months or more - unrealized loss	(13.0)	(25.0)
Unrealized loss position 12 months or more - fair value	879.0	1,094.0
Total unrealized loss	(16.0)	(128.0)
Total fair value	1,541.0	12,893.0
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(6.0)	(3.0)
Unrealized loss position less than 12 months - fair value	344.0	368.0
Unrealized loss position 12 months or more - unrealized loss	(74.0)	(85.0)
Unrealized loss position 12 months or more - fair value	1,292.0	1,527.0
Total unrealized loss	(80.0)	(88.0)
Total fair value	1,636.0	1,895.0
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(2.0)	(7.0)
Unrealized loss position less than 12 months - fair value	122.0	745.0
Unrealized loss position 12 months or more - unrealized loss	(1.0)	(3.0)
Unrealized loss position 12 months or more - fair value	186.0	120.0
Total unrealized loss	(3.0)	(10.0)
Total fair value	308.0	865.0
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(5.0)	(22.0)
Unrealized loss position less than 12 months - fair value	1,006.0	2,310.0
Unrealized loss position 12 months or more - unrealized loss	(20.0)	(7.0)
Unrealized loss position 12 months or more - fair value	1,169.0	807.0
Total unrealized loss	(25.0)	(29.0)
Total fair value	2,175.0	3,117.0
Asset backed [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(8.0)	(30.0)
Unrealized loss position less than 12 months - fair value	1,081.0	3,477.0
Unrealized loss position 12 months or more - unrealized loss	(32.0)	(18.0)
Unrealized loss position 12 months or more - fair value	1,567.0	494.0
Total unrealized loss	(40.0)	(48.0)
Total fair value	2,648.0	3,971.0
State and Municipal [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(3.0)	(3.0)
Unrealized loss position less than 12 months - fair value	239.0	326.0
Unrealized loss position 12 months or more - unrealized loss	(0.5)	(2.0)
Unrealized loss position 12 months or more - fair value	55.0	60.0
Total unrealized loss	(3.0)	(5.0)
Total fair value	294.0	386.0
Other Debt Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(2.0)	(8.0)
Unrealized loss position less than 12 months - fair value	79.0	759.0
Unrealized loss position 12 months or more - unrealized loss	(2.0)	(4.0)
Unrealized loss position 12 months or more - fair value	102.0	188.0
Total unrealized loss	(4.0)	(12.0)
Total fair value	181.0	947.0
Corporate Stocks And Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss		(0.5)
Unrealized loss position less than 12 months - fair value		46.0
Unrealized loss position 12 months or more - unrealized loss	(0.5)	(1.0)
Unrealized loss position 12 months or more - fair value	15.0	15.0
Total unrealized loss	(0.5)	(1.0)
Total fair value	$ 15.0	$ 61.0