Stock Options (Details 2)	1 Months Ended						12 Months Ended
	Oct. 31, 2013	Apr. 30, 2013	Oct. 31, 2012	Apr. 30, 2012	Oct. 31, 2011	Apr. 30, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Option [Line Items]
Expected volatility		26.34%	26.34%	36.28%	32.02%	22.17%	34.30%	40.00%	42.00%
Expected term (in years)		6 months	6 months	6 months	6 months	6 months	4 years	4 years	4 years 1 month 6 days
Risk-free interest rate		0.15%	0.15%	0.35%	0.12%	0.20%	0.80%	0.80%	1.50%