Accounts Payable and Accrued Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Accounts Payable And Accrued Liabilities [Line Items]
Asset retirement obligation, accretion expense	$ 1.7	$ 0.7
Compact and Federal LLRW Disposal Facilities
Accounts Payable And Accrued Liabilities [Line Items]
Asset Retirement Obligation		$ 19.1