Fair Value Measurements Categorization of Investments and Certain Other Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | $112,088 | | $113,972 | |
Corporate Bonds, Municipal Bonds and Other Debt Securities [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 32,320 | [1] | 33,882 | [1] |
Securities Investments [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 16,050 | [1] | 14,399 | [1] |
Mutual Funds [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 5,535 | | 9,380 | |
Financial Instruments Owned and Pledged as Collateral at Fair Value [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 58,183 | | 56,311 | |
Treasury Bills, Municipal Bonds and Commercial Paper [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Cash and Cash Equivalents | 11,304 | | 14,254 | |
Level I [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 78,097 | | 77,692 | |
Cash and Cash Equivalents | 112,760 | | 284,199 | |
Level I [Member] | Corporate Bonds, Municipal Bonds and Other Debt Securities [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | [1] | 0 | [1] |
Level I [Member] | Securities Investments [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 14,379 | [1] | 12,001 | [1] |
Level I [Member] | Mutual Funds [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 5,535 | | 9,380 | |
Level I [Member] | Financial Instruments Owned and Pledged as Collateral at Fair Value [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 58,183 | | 56,311 | |
Level II [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 33,991 | | 36,280 | |
Cash and Cash Equivalents | 0 | | 0 | |
Level II [Member] | Corporate Bonds, Municipal Bonds and Other Debt Securities [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 32,320 | [1] | 33,882 | [1] |
Level II [Member] | Securities Investments [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 1,671 | | 2,398 | [1] |
Level II [Member] | Mutual Funds [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | | 0 | |
Level II [Member] | Financial Instruments Owned and Pledged as Collateral at Fair Value [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | | 0 | |
Level III [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | | 0 | |
Cash and Cash Equivalents | 0 | | 0 | |
Level III [Member] | Corporate Bonds, Municipal Bonds and Other Debt Securities [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | [1] | 0 | [1] |
Level III [Member] | Securities Investments [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | | 0 | [1] |
Level III [Member] | Mutual Funds [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | 0 | | 0 | |
Level III [Member] | Financial Instruments Owned and Pledged as Collateral at Fair Value [Member] | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total Assets Measured At Fair Value | $0 | | $0 | |
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[1] | Includes $11,304 and $14,254 of treasury bills, municipal bonds and commercial paper classified within Cash and Cash Equivalents on the Unaudited Condensed Consolidated Statements of Financial Condition as of MarchB 31, 2014 and DecemberB 31, 2013, respectively. |