Investment Securities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Debt securities transferred from AFS to HTM	$ 24,700
Unrealized loss	227
Assets	243,274		$ 223,383
Trust Deposits [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair value of pledged securities	923
FHLB [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair value of pledged securities	24,200
Federal Reserve Bank [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair value of pledged securities	$ 2,500
Scenario, Forecast [Member]
Schedule of Held-to-maturity Securities [Line Items]
Assets		$ 250,000