Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Accrued earnouts	$ 7.0		$ 7.0		$ 9.8
Performance targets, maximum potential obligation	13.4		13.4
Impairment charge recognized, related to long-lived assets	6.5	0.6	10.2	1.0
Certificate of deposits	5.2		5.2		5.3
Held-to-maturity investments, carrying value	1.3		1.3		1.3
Held-to-maturity investments, fair value	$ 1.5		$ 1.5		$ 1.5
Interest rate under Revolving Credit Facility			1.875%