Financial Instruments Owned and Pledged as Collateral at Fair Value, Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase - Additional Information (Details)	9 Months Ended
	Sep. 30, 2017
Banking and Thrift [Abstract]
Securities Average Estimated Maturity Period (in years)	1 year 3 months 18 days
Confidence Level Value at Risk	98.00%
Value at Risk Threshold	0.10%