Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Contractual interest rate for funds borrowed, under the debt agreement.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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Debt (non-printing) (Detail) $ in Millions		3 Months Ended
Debt (non-printing) (Detail) $ in Millions	Mar. 06, 2012	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015
Debt Instrument [Line Items]
Interest expense related to contractual interest coupon of convertible notes		$ 1.3	$ 1.3
Convertible Debt \| 1.75% Senior Notes due 2017
Debt Instrument [Line Items]
Interest rate		1.75%		1.75%
Senior Notes \| 7 1⁄2% Senior Notes due 2022
Debt Instrument [Line Items]
Interest rate		7.50%		7.50%
4.20% Building Loan
Debt Instrument [Line Items]
Interest rate		4.20%
1 3⁄4% Senior Convertible Notes due 2017
Debt Instrument [Line Items]
Initial conversion rate of common stock	0.0234449	1