Investment Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Carrying value of securities pledged to secure public deposits, derivatives and other secured borrowings | $	$ 925,000,000	$ 1,040,000,000
Number of available for sale securities in unrealized loss position | security	277
Number of held-to-maturity securities in unrealized loss position | security	67
Other-than-temporary impairment charges | $	$ 0	$ 0	$ 0