Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
Increase (decrease) in liability for unrecognized tax benefits within the next twelve months	$ (27.9)
Uncertain tax position, accrued interest	5.2	4.4
Obligations of states and state agencies [Member]
Income Taxes [Line Items]
Operating loss carryforwards	926
Incremental state tax provision (expense)			8.5
Obligations of states and state agencies [Member] | Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration dates	Jan. 01, 2014
Obligations of states and state agencies [Member] | Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration dates	Dec. 31, 2031
Federal [Member]
Income Taxes [Line Items]
Alternative minimum tax credit carryforward	$ 1.6