Variable Interest Entities - Carrying Amounts related to Unconsolidated VIEs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entities
Carrying amount of liabilities assumed	$ 601	$ 0	$ 0
Interest bearing deposits in banks	1,335	3,844
Unconsolidated Assets
Securities Available for Sale	17,563	14,141
Loans held for investment	80,014	77,551
Other Assets	8,800	8,496
Unconsolidated Liabilities
Other Liabilities	2,143	2,520
Unconsolidated VIEs
Variable Interest Entities
Interest bearing deposits in banks	1	1
Unconsolidated Assets
Securities Available for Sale	29	37
Loans held for investment	276	239
Other Assets	2,799	2,941
Total Assets	3,105	3,218
Unconsolidated Liabilities
Other Liabilities	307	447
Total Liabilities	307	447
Maximum Exposure to Loss	3,208	3,271
Unconsolidated VIEs | LIHC investments
Variable Interest Entities
Carrying amount of liabilities assumed	55	125	$ 177
Interest bearing deposits in banks	0	0
Unconsolidated Assets
Securities Available for Sale	29	25
Loans and Leases Receivable, Net of Deferred Income		168
Loans held for investment	228
Other Assets	1,028	1,164
Total Assets	1,285	1,357
Unconsolidated Liabilities
Other Liabilities	254	381
Total Liabilities	254	381
Maximum Exposure to Loss	1,284	1,357
Unconsolidated VIEs | Leasing investments
Variable Interest Entities
Interest bearing deposits in banks	1	1
Unconsolidated Assets
Securities Available for Sale	0	12
Loans and Leases Receivable, Net of Deferred Income		47
Loans held for investment	24
Other Assets	1,745	1,751
Total Assets	1,770	1,811
Unconsolidated Liabilities
Other Liabilities	53	66
Total Liabilities	53	66
Maximum Exposure to Loss	1,792	1,833
Unconsolidated VIEs | Other investments
Variable Interest Entities
Interest bearing deposits in banks	0	0
Unconsolidated Assets
Securities Available for Sale	0	0
Loans and Leases Receivable, Net of Deferred Income		24
Loans held for investment	24
Other Assets	26	26
Total Assets	50	50
Unconsolidated Liabilities
Other Liabilities	0	0
Total Liabilities	0	0
Maximum Exposure to Loss	$ 132	$ 81