Securities, Unrealized Gains (Losses) Related to Equity Securities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Issuer	Dec. 31, 2017 Issuer
Gains and losses on equity securities [Abstract]
Net gains and losses recognized on equity securities	$ 72
Less: Net gains and losses recognized during the period on equity securities sold during the period	44
Unrealized gains and losses recognized on equity securities still held at March 31, 2017	28
Carrying amount of equity securities without readily determinable fair values	5,000
Impairment adjustments of equity securities without readily determinable fair values	0
Downward adjustments of equity securities without readily determinable fair values	0
Upward adjustments of equity securities without readily determinable fair values	$ 0
Number of issuers whose holdings exceeded 10% of consolidated stockholders' equity, excluding U.S. Government securities | Issuer	0	0