Regulatory Capital Requirements - Capital Conservation Buffer (Details)	Sep. 30, 2019	Dec. 31, 2018	Jan. 01, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Effective CET1 capital to risk-weighted assets (as a percent)	4.50%	4.50%
Effective Tier 1 capital to risk-weighted assets (as a percent)	12.15%	11.97%
Effective total capital to risk-weighted assets (as a percent)	13.11%	12.99%
Capital conservation buffer
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Phased in rate (as a percent)			0.625%
Annual increase after initial year (as a percent)	0.625%
Capital requirements above regulatory rate (as a percent)	2.50%
Effective CET1 capital to risk-weighted assets (as a percent)	7.00%
Effective Tier 1 capital to risk-weighted assets (as a percent)	8.50%
Effective total capital to risk-weighted assets (as a percent)	10.50%