Fair Value Measurements - Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Total Fair Value Inputs [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	$ 334	$ 318
Mid Capitalization Registered Investment Companies	85	83
Small Capitalization Registered Investment Companies	71	68
International Developed And Emerging Markets Registered Investment Companies	174	168
Fixed Income Registered Investment Companies	49	50
Fixed General Account	171	177
Interest Rate Derivatives		418
Acquisition-related Consideration	8,471	8,898
Liabilities, Fair Value Disclosure	9,355	10,180
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Large Capitalization Registered Investment Companies	334	318
Mid Capitalization Registered Investment Companies	85	83
Small Capitalization Registered Investment Companies	71	68
International Developed And Emerging Markets Registered Investment Companies	174	168
Fixed Income Registered Investment Companies	49	50
Fixed General Account	0	0
Interest Rate Derivatives		0
Acquisition-related Consideration	0	0
Liabilities, Fair Value Disclosure	713	687
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	171	177
Interest Rate Derivatives		418
Acquisition-related Consideration	0	0
Liabilities, Fair Value Disclosure	171	595
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
Acquisition-related Consideration	8,471	8,898
Liabilities, Fair Value Disclosure	$ 8,471	$ 8,898