Disclosures About Offsetting Assets And Liabilities (Financial Assets And Derivative Assets That Are Subject To Offset) (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Offsetting [Abstract]
Gross amounts of recognized assets, Securities borrowing	[1]	$ 170,165	$ 132,776
Net amounts presented in the Statement of Financial Condition, Securities borrowing	[1]	170,165	132,776
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Securities borrowing	[1]	(47,974)	(78,474)
Gross amounts not offset in the Statement of Financial Position, Collateral received, Securities borrowing	[1]	(110,088)	(37,248)
Securities borrowed, Net amount	[1]	12,103	17,054
Gross amounts of recognized assets, Reverse repurchase agreements	[2]	622,361	512,220
Net amounts presented in the Statement of Financial Condition, Securities purchased under agreements to resell	[2]	622,361	512,220
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Securities purchased under agreements to resell	[2]	(261,773)	(233,624)
Gross amounts not offset in the Statement of Financial Position, Collateral received, Securities purchased under agreements to resell	[2]	(356,842)	(266,008)
Securities purchased under agreements to resell, Net amount	[2]	3,746	12,588
Gross amounts of recognized assets, Cash flow interest rate contracts		11,117	7,995
Net amounts presented in the Statement of Financial Condition, Cash flow interest rate contracts		11,117	7,995
Cash flow interest rate contracts, Net amount		11,117	7,995
Gross amounts of recognized assets		803,643	652,991
Net amounts presented in the Statements of Financial Condition		803,643	652,991
Gross amounts not offset in the Statement of Financial Position		(309,747)	(312,098)
Gross amounts not offset in the Statement of Financial Position, Collateral received		(466,930)	(303,256)
Net amount		$ 26,966	$ 37,637

[1] Securities borrowing transactions are included in receivables from brokers, dealers, and clearing organizations on the consolidated statements of financial condition. See Note 3 in the notes to consolidated financial statements for additional information on receivables from brokers, dealers, and clearing organizations.

[2] Collateral received includes securities received by our company from the counterparty. These securities are not included on the consolidated statements of financial condition unless there is an event of default. The fair value of securities pledged as collateral was $621.5 million and $509.4 million at September 30, 2018 and December 31, 2017, respectively.