Capital Ratios (Details) - USD ($) $ in Billions	Jan. 01, 2016	Sep. 30, 2018	Jun. 30, 2018	May 24, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2013
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		19.59%			19.51%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	0.625%					2.50%
Maximum amount of assets to exempt banks				$ 10
Maximum amount of assets for qualified bank holding companies		$ 3	$ 1
CET 1 ratio		17.37%			17.11%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)		15.53%			14.62%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)		18.91%			18.73%		6.00%
Term of mandatory compliance	4 years
Minimum
Community bank leverage ratio				8.00%
CET 1 ratio		7.00%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)						4.50%	4.00%
Maximum
Community bank leverage ratio				10.00%