Fair Value Measurements (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Fair Value Measurements [Line Items]
Estimated fair value of performance targets	$ 9.2		$ 9.2		$ 5.5
Performance targets, maximum potential obligation	18.2		18.2
Impairment recognized, related to long-lived assets	1.6	1.1	2.6	1.4
Certificate of deposits	5.3		5.3		5.6
Held-to-maturity investments, carrying value	1.3		1.3		1.4
Held-to-maturity investments, fair value	$ 1.5		$ 1.5		$ 1.6