Fair Value Of Financial Instruments (Estimated Fair Values Of Financial Instruments Not Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities purchased under agreements to resell	$ 470,025	$ 217,930
Held-to-maturity securities	4,765,024	4,107,960
Securities sold under agreements to repurchase	208,228	190,955
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	1,402,921	2,245,082
Cash segregated for regulatory purposes	95,074	172,932
Securities purchased under agreements to resell	470,025	217,930
Held-to-maturity securities	4,765,024	4,107,960
Bank loans	12,168,119	11,088,058
Loans held for sale	330,521	551,248
Securities sold under agreements to repurchase	208,228	190,955
Bank deposits	18,527,784	17,192,722
Senior notes	1,228,983	1,265,669
Debentures to Stifel Financial Capital Trusts	46,444	41,071
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	1,402,921	2,245,082
Cash segregated for regulatory purposes	95,074	172,932
Securities purchased under agreements to resell	424,621	164,094
Senior notes	1,228,983	1,265,669
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities purchased under agreements to resell	45,404	53,836
Held-to-maturity securities	4,598,600	3,943,944
Bank loans	12,168,119	11,088,058
Loans held for sale	330,521	551,248
Securities sold under agreements to repurchase	208,228	190,955
Bank deposits	18,527,784	17,192,722
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity securities	166,424	164,016
Debentures to Stifel Financial Capital Trusts	$ 46,444	$ 41,071