Convertible Senior Notes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			2 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2016	Jun. 30, 2014	Jul. 31, 2013	Feb. 28, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Long term debt, face amount					$ 167,727		$ 206,865
Payment for repurchase of convertible notes					24,052	$ 1,940
Gain recognized on retirement of debt						60
Amortization of debt issuance costs recognized as interest expense					300	$ 400
4.875% Convertible Senior Notes (due 2020)
Debt Instrument [Line Items]
Long term debt, face amount		$ 115,000			$ 113,000		$ 113,000
Debt instrument, interest rate		4.875%			4.875%		4.875%
Debt instrument, maturity date		Jun. 01, 2020
Frequency of interest payment					Semi-annually
Conversion rate in share per $1000 principal amount of notes		103.7613
Debt instrument, conversion rate		$ 9.64
Debt instrument repurchase amount	$ 2,000
Write-off of debt issuance costs	100
Gain recognized on retirement of debt	$ 100
Convertible senior note payable, fair value					$ 112,500		$ 89,300
Debt instrument, maturity year					2020		2020
4.25% Convertible Senior Notes (due 2018)
Debt Instrument [Line Items]
Long term debt, face amount			$ 100,000		$ 54,727		$ 93,865
Debt instrument, interest rate			4.25%		4.25%		4.25%
Debt instrument, maturity date			Aug. 01, 2018
Frequency of interest payment					Semi-annually
Conversion rate in share per $1000 principal amount of notes			114.3674
Debt instrument, conversion rate			$ 8.74
Debt instrument repurchase amount			$ 39,100		$ 6,100
Write-off of debt issuance costs					100
Payment for repurchase of convertible notes			$ 24,100
Convertible senior note payable, fair value					$ 55,500		$ 83,700
Debt instrument, maturity year					2018		2018
4.25% Convertible Senior Notes (due 2018) | Common Stock
Debt Instrument [Line Items]
Debt instrument repurchase amount				$ 39,100
Debt instrument shares common stock issued upon conversion			2,865,000	2,865,000