Disclosures About Offsetting Assets And Liabilities (Financial Assets And Derivative Assets That Are Subject To Offset) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Disclosures About Offsetting Assets And Liabilities [Abstract]
Gross amounts of recognized assets, Securities borrowing	$ 333,371	[1]	$ 153,819	[1]
Gross amounts offset in the Statement of Financial Condition, Securities borrowing		[1]		[1]
Net amounts presented in the Statement of Financial Condition	333,371	[1]	153,819	[1]
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Securities borrowing		[1]		[1]
Gross amounts not offset in the Statement of Financial Position, Collateral received, Securities borrowing	(333,371)	[1]	(153,819)	[1]
Gross amounts of recognized assets, Securities purchased under agreements to resell	156,341		158,695
Gross amounts offset in the statement of Financial Condition, Securities purchased under agreements to resell
Net amounts presented in the Statement of Financial Condition, Securities purchased under agreements to resell	156,341		158,695
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Securities purchased under agreements to resell
Gross amounts not offset in the Statement of Financial Position, Collateral received, Securities purchased under agreements to resell	(156,341)		(158,695)
Gross amounts of recognized assets, Cash flow interest rate contracts
Gross amounts offset in the Statement of Financial Condition, Cash flow interest rate contracts
Net amounts presented in the Statement of Financial Condition
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Cash flow interest rate contracts
Gross amounts not offset in the Statement of Financial Position, Financial instruments, Cash flow interest rate contracts
Cash flow interest rate contracts, Net amount
Gross amounts of recognized assets	489,712		312,514
Gross amounts offset in the Statement of Financial Condition
Net amounts presented in the Statements of Financial Condition	489,712		312,514
Gross amounts not offset in the Statement of Financial Position
Gross amounts not offset in the Statement of Financial Position, Collateral received	$ (489,712)		$ (312,514)

[1] Securities borrowing transactions are included in receivables from brokers, dealers, and clearing organizations on the consolidated statements of financial condition. See Note 4 in the notes to our consolidated financial statements for additional information on receivables from brokers, dealers, and clearing organizations.(2)