Commitments, Contingencies and Legal Matters - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Feb. 28, 2009	Sep. 30, 2012	Dec. 31, 2011
Contingencies And Commitments [Line Items]
Total purchase commitments due through 2016		$ 384.6
Company's percentage of take-or-pay agreement with SMP		51.00%
Terms in which take-or-pay agreement may be terminated by either party		Upon two years written notice
Outstanding obligation related to standby letters of credit		4.4	3.5
Jury award to GE for patent infringement	$ 7.6