Fair Value Measurements - Nature of Investments and Related Liquidation Restrictions (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
NAV of investments at fair value
Fair Value	$ 220.7		$ 214.1
Unfunded Commitments	73.1		62.9
Private equity fund-of-funds [Member]
NAV of investments at fair value
Fair Value	135.9	[1]	131.8	[1]
Unfunded Commitments	73.1	[1]	62.9	[1]
Other funds [Member]
NAV of investments at fair value
Fair Value	84.8	[2]	82.3	[2]
Unfunded Commitments	$ 0	[2]	$ 0	[2]

[1] These funds primarily invest in a broad range of private equity funds, as well as making direct investments. Distributions will be received as the underlying assets are liquidated over the life of the funds.

[2] These are multi-disciplinary funds that invest across various asset classes and strategies, including long/short equity, credit and real estate. Investments are generally redeemable on a daily or quarterly basis.