Variable Interest Entities (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2016
Variable Interest Entities
Interest bearing deposits in banks	$ 2,749		$ 6,696
Unconsolidated Assets
Securities available for sale	14,344		13,011
Loans Held for Investment	77,599		79,299	[1]
Other Assets	5,387	$ 4,640	5,322
Unconsolidated Liabilities
Other liabilities	2,017	1,891	2,203
Unconsolidated VIEs
Variable Interest Entities
Interest bearing deposits in banks	5		5
Unconsolidated Assets
Securities available for sale	25		25
Loans Held for Investment	289		244
Other Assets	2,376		2,390
Total Assets	2,695		2,664
Unconsolidated Liabilities
Other liabilities	485		481
Total Liabilities	485		481
Maximum Exposure to Loss	2,716		2,710
Unconsolidated VIEs | LIHC investments
Variable Interest Entities
Interest bearing deposits in banks	0		0
Liabilities Assumed	37	$ 32
Unconsolidated Assets
Securities available for sale	25		25
Loans Held for Investment	220		190
Other Assets	1,166		1,169
Total Assets	1,411		1,384
Unconsolidated Liabilities
Other liabilities	424		420
Total Liabilities	424		420
Maximum Exposure to Loss	1,411		1,384
Unconsolidated VIEs | Leasing Investments
Variable Interest Entities
Interest bearing deposits in banks	5		5
Unconsolidated Assets
Securities available for sale	0		0
Loans Held for Investment	20		20
Other Assets	1,200		1,194
Total Assets	1,225		1,219
Unconsolidated Liabilities
Other liabilities	61		61
Total Liabilities	61		61
Maximum Exposure to Loss	1,245		1,240
Unconsolidated VIEs | Other investments
Variable Interest Entities
Interest bearing deposits in banks	0		0
Unconsolidated Assets
Securities available for sale	0		0
Loans Held for Investment	49		34
Other Assets	10		27
Total Assets	59		61
Unconsolidated Liabilities
Other liabilities	0		0
Total Liabilities	0		0
Maximum Exposure to Loss	$ 60		$ 86

[1] Includes $109 million and $100 million at March 31, 2016 and December 31, 2015, respectively, for net unamortized (discounts) and premiums and deferred (fees) and costs.