SECURITIES - Schedule of Securities Under Agreements to Repurchase or Resell Remaining Contractual Maturity (Details) - Mortgage-backed securities - Agency $ in Millions	Jun. 30, 2015 USD ($)
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 3,050
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	0
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	250
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,000
Greater Than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 1,800