Premises and Equipment - Premises and Equipment Carried at Cost (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Premises and Equipment
Cost	$ 1,740	$ 1,732
Accumulated Depreciation and Amortization	(1,132)	(1,111)
Net Book Value	608	621
Land
Premises and Equipment
Cost	140	148
Accumulated Depreciation and Amortization	0	0
Net Book Value	140	148
Premises
Premises and Equipment
Cost	598	601
Accumulated Depreciation and Amortization	(342)	(334)
Net Book Value	256	267
Leasehold improvements
Premises and Equipment
Cost	331	301
Accumulated Depreciation and Amortization	(236)	(230)
Net Book Value	95	71
Furniture, fixtures and equipment
Premises and Equipment
Cost	671	682
Accumulated Depreciation and Amortization	(554)	(547)
Net Book Value	$ 117	$ 135