Investments - Additional Information (Detail) € in Millions, $ in Millions |
12 Months Ended | ||||
---|---|---|---|---|---|
Dec. 31, 2015
USD ($)
|
Dec. 31, 2014
USD ($)
|
Dec. 31, 2013
USD ($)
|
Apr. 09, 2013
USD ($)
|
Apr. 09, 2013
EUR (€)
|
|
Investment [Line Items] | |||||
Realized gain on trading securities | $ 0.4 | $ 8.2 | $ 1.0 | ||
Interest acquired in limited partnership | 5.0 | ||||
Percentage of noncontrolling equity interest acquired | 50.00% | ||||
Maximum [Member] | |||||
Investment [Line Items] | |||||
Future capital commitment | $ 4.9 | ||||
Kleinwort Benson Investors International, Ltd. [Member] | |||||
Investment [Line Items] | |||||
Percentage of noncontrolling equity interest acquired | 24.00% | 24.00% | |||
Noncontrolling equity interest acquired, amount | $ 3.4 | € 2.6 |