Consolidated Investment Products (Level 3 Valuation Techniques) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2016
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liabilities	$ 16,210,200,000	$ 15,966,400,000
Private Equity Fund, Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	320,000,000
Private Equity Funds, Priced Using Private Market Transactions [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	61,200,000
Private Equity Funds, Priced Using Third Party Appraisal [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	7,300,000
Debt Securities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Investments, Fair Value Disclosure	31,700,000
Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Investments, Fair Value Disclosure	0
Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Investments, Fair Value Disclosure	0
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Investments, Fair Value Disclosure	31,700,000
Private Equity Funds [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	368,200,000	62,600,000
Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	0	0
Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets	0	0
Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private Equity Fund Assets		$ 0
Market Comparable [Member] | Minimum [Member] | Private Equity Fund, Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Revenue Multiple	0.00%
Derivative Discount Rate	25.00%
Published valuation and/or broker quotes for similar types of assets	$ 25,000,000
Market Comparable [Member] | Maximum [Member] | Private Equity Fund, Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Revenue Multiple	0.00%
Derivative Discount Rate	50.00%
Published valuation and/or broker quotes for similar types of assets	$ 101,000,000
Market Comparable [Member] | Weighted Average [Member] | Private Equity Fund, Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Revenue Multiple	320.00%
Derivative Discount Rate	25.00%
Published valuation and/or broker quotes for similar types of assets	$ 44,400,000