Long Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified		1 Months Ended										1 Months Ended		1 Months Ended
	Jan. 18, 2013	Jan. 31, 2013 Minimum	Jan. 31, 2013 Maximum	Jan. 31, 2013 Federal funds rate	Jan. 31, 2013 One Month LIBOR Rate	Jan. 18, 2013 LIBOR Loans Minimum	Jan. 18, 2013 LIBOR Loans Maximum	Jan. 18, 2013 Base Rate Loans Minimum	Jan. 18, 2013 Base Rate Loans Maximum	Jan. 31, 2013 Standby Letters of Credit	Apr. 30, 2012 Standby Letters of Credit	Jan. 31, 2013 Revolving Credit Facility	Jan. 18, 2013 Revolving Credit Facility	Jan. 31, 2013 Revolving Credit Facility Letter of Credit
Debt Disclosure [Line Items]
Senior Unsecured Revolving Facility, aggregate availability													$ 75
Senior Unsecured Revolving Facility, additional borrowing capacity												50		15
Senior Unsecured Revolving Facility, maturity date												Jan. 18, 2018
Applicable margin on variable interest rate				1.50%	1.50%	0.50%	1.50%	0.00%	0.25%
Quarterly Commitment Fees on the Facility's unused commitments		0.25%	0.35%
Financial covenants amount	50
Previous Facility, standby letters of credit										2.7	2.9
Previous Facility, restricted cash										$ 2.9	$ 10.0