Fair Value Measurements - Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Total Fair Value Inputs [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	$ 369	$ 336
Mid Capitalization Registered Investment Companies	102	88
Small Capitalization Registered Investment Companies	87	72
International Developed And Emerging Markets Registered Investment Companies	193	187
Fixed Income Registered Investment Companies	44	48
Fixed General Account	165	173
Interest Rate Derivatives	0	0
Acquisition-related Consideration	5,921	4,901
Liabilities, Fair Value Disclosure	6,881	5,805
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	369	336
Mid Capitalization Registered Investment Companies	102	88
Small Capitalization Registered Investment Companies	87	72
International Developed And Emerging Markets Registered Investment Companies	193	187
Fixed Income Registered Investment Companies	44	48
Fixed General Account	0	0
Interest Rate Derivatives	0	0
Acquisition-related Consideration	0	0
Liabilities, Fair Value Disclosure	795	731
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	0	0
Mid Capitalization Registered Investment Companies	0	0
Small Capitalization Registered Investment Companies	0	0
International Developed And Emerging Markets Registered Investment Companies	0	0
Fixed Income Registered Investment Companies	0	0
Fixed General Account	165	173
Interest Rate Derivatives	0	0
Acquisition-related Consideration	0	0
Liabilities, Fair Value Disclosure	165	173
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	0	0
Mid Capitalization Registered Investment Companies	0	0
Small Capitalization Registered Investment Companies	0	0
International Developed And Emerging Markets Registered Investment Companies	0	0
Fixed Income Registered Investment Companies	0	0
Fixed General Account	0	0
Interest Rate Derivatives	0	0
Acquisition-related Consideration	5,921	4,901
Liabilities, Fair Value Disclosure	$ 5,921	$ 4,901