Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Jul. 31, 2010	Jun. 30, 2010	Sep. 30, 2013	Mar. 31, 2010
Commitments And Contingencies Disclosure [Abstract]
Contingent liabilities under outstanding letters of credit			$ 7.4
Contingently liable for performance, current			16.1
Notice of deficiency received for taxes and penalties related to IRS audit		71.5
Notice of deficiency received for taxes and penalties including interest		98.7
Taxes and penalties including interest deposited with IRS	23.7	75.0
Notice of deficiency received for taxes and penalties including interest, net outlay	97.9
Taxes and penalties amount refunded from IRS	0.8
Total taxes and penalties including interest deposited with IRS	98.7
Assessment of income tax				8.1
Assessment of penalties				1.9
Income tax interest accrued			$ 2.3