Regulatory Capital Matters - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Capital conservation buffer				1.25%	0.625%	0.00%
Capital conservation buffer description	The capital conservation buffer is being phased in from 0.0% for 2015 to 2.50% by 2019. The capital conservation buffers for 2016, 2017 and 2018 are 0.625%, 1.25% and 1.875%, respectively.
Scenario Forecast
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Capital conservation buffer		2.50%	1.875%