Accumulated Other Comprehensive (Loss) Income - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified to earnings from the change in fair value of derivatives component of accumulated other comprehensive income	$ 3.1	$ 5.1	$ 6.2
Estimated reclassification of change in fair value of derivatives component of accumulated other comprehensive (loss) income to earning during the next twelve months	(2.6)
Amounts expected to be recognized as components of net periodic benefit costs, net actuarial loss	7.8
Amounts expected to be recognized as components of net periodic benefit costs, net prior service credit	$ (0.4)