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Debt - Convertible Senior Notes - Additional Information (Detail) (USD $)
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0 Months Ended |
3 Months Ended |
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Mar. 15, 2013
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Mar. 31, 2015
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Mar. 15, 2013
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| Debt Instrument [Line Items] |
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| Convertible senior notes, maturity date |
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Apr. 01, 2019 |
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| Scenario 1 |
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| Debt Instrument [Line Items] |
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| Convertible trading days |
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20 |
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| Convertible threshold consecutive trading days |
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30 days |
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| Threshold percentage of stock price trigger |
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130.00% |
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| Scenario 2 |
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| Debt Instrument [Line Items] |
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|
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| Convertible threshold consecutive trading days |
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5 days |
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| Threshold percentage of stock price trigger |
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98.00% |
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| Debt instrument convertible threshold business period |
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5 days |
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| Senior Convertible Notes |
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| Debt Instrument [Line Items] |
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| Issuance date |
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Mar. 15, 2013 |
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| Principal amount |
$ 201,250,000.00 |
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$ 201,250,000.00 |
| Debt instrument additional issued principal amount |
26,250,000.00 |
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26,250,000.00 |
| Convertible senior notes, maturity date |
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Apr. 01, 2019 |
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| Interest rate |
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4.25% |
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| Frequency of periodic payment |
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semi-annually |
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| Date of first required payment |
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Oct. 01, 2013 |
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| Proceeds from debt, net of issuance costs |
194,800,000 |
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| Earliest convertible date |
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Jul. 01, 2013 |
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| Convertible notes amount in multiples |
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1,000 |
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| Latest convertible date |
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Mar. 28, 2019 |
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| Conversion ratio |
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0.0461723 |
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| Conversion price |
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$ 21.66 |
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| Redemption period start date |
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Apr. 06, 2016 |
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| Redemption price, percentage of principal amount redeemed |
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100.00% |
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| Convertible effective interest rate |
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6.50% |
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| Carrying amount of equity component |
22,300,000 |
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22,300,000 |
| Debt issuance costs |
6,400,000 |
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| Debt issuance costs liability component |
$ 5,700,000 |
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| Remaining discount amortization period |
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6 years |
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