Regulatory Requirements And Capital Ratios (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Parent Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, ratio, required to be well-capitalized	10.00%	10.00%
Cash balance	$ 59,031	$ 26,520
CET1 ratio, minimum capital required basel III phase in schedule	5.75%	5.125%
Total capital, ratio, minimum capital required basel iIII phase in schedule	9.25%	8.625%
Tier 1, ratio, minimum capital required basel III phase in schedule	7.25%	6.625%
CET1 ratio	15.10%	13.30%
Tier I capital, ratio	15.70%	13.90%
Tier I Leverage Ratio, Average Assets	11.00%	10.10%
City National
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, ratio, required to be well-capitalized	10.00%	10.00%
Dividends Available Without Regulatory Approval	$ 75,000
CET1 ratio, minimum capital required basel III phase in schedule	5.75%	5.125%
Total capital, ratio, minimum capital required basel iIII phase in schedule	9.25%	8.625%
Tier 1, ratio, minimum capital required basel III phase in schedule	7.25%	6.625%
CET1 ratio	12.00%	11.20%
Tier I capital, ratio	12.00%	11.50%
Tier I Leverage Ratio, Average Assets	8.50%	8.30%