Non-Marketable Investments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying value of the Company's non-marketable investments		$ 4.3		$ 5.7
Gain (loss) from non-marketable investments	0.1	0.1	(0.1)
Book value of investment		0.9		0.9
Gross distributions received from funds			0.2
Gross distributions received from cost and equity method investment		$ 1.4
Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Ownership interest of Company		5.00%