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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Amount of interest expense incurred on long-term debt classified as other, including, but not limited to, interest on long-term notes and amortization of issuance costs.

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Convertible Notes (Interest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 16, 2013	Jun. 29, 2009
Interest expense related to notes
Additional paid in capital	$ 1,181,230	$ 1,130,368
Convertible Senior Notes [Member] \| 1.125% Convertible Senior Notes due 2018
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.125%	1.125%	1.125%	1.125%
Convertible Senior Notes [Member] \| 5% Convertible Senior Notes due 2014
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			5.00%
Convertible notes
Interest expense related to notes
Total interest expense on convertible notes	$ 8,302	$ 7,939	$ 20,259
Additional paid in capital	93,400	93,400
Convertible notes \| 1.125% Convertible Senior Notes due 2018
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				1.125%
Interest expense related to notes
Coupon interest	1,553	1,567	1,567
Amortization of discount at an additional effective interest rate	$ 6,749	$ 6,372	$ 6,019
Debt Instrument, Interest Rate, Effective Percentage	5.50%	5.50%	5.50%
Convertible notes \| 5% Convertible Senior Notes due 2014
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					5.00%
Interest expense related to notes
Coupon interest	$ 0	$ 0	$ 3,929
Amortization of discount at an additional effective interest rate	$ 0	$ 0	$ 8,744
Debt Instrument, Interest Rate, Effective Percentage			11.70%