Subsequent Event - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	2 Months Ended	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Subsequent Event [Line Items]
Principal amount of convertible notes surrendered for conversion			$ 0.7
Scenario, Forecast [Member]
Subsequent Event [Line Items]
Principal amount of convertible notes surrendered for conversion	90.3	90.3
Number of trading days cash settlement averaging periods	20 days	20 days
Estimated cash payment for convertible notes	$ 90.3	$ 90.3