Convertible Notes (Tables)

12 Months Ended

Dec. 31, 2012

Debt Disclosure [Abstract]

Schedule of convertible notes

(Dollars in thousands)	As of December 31, 2012			As of December 31, 2011
5% Convertible Senior Notes due 2014 (the "2014 Notes")	$	172,500		$	172,500
Unamortized discount	(24,944		)	(39,007		)
Total convertible notes	$	147,556		$	133,493
Less current portion	—			—
Total long-term convertible notes	$	147,556		$	133,493

Schedule of interest expense on notes

	Years Ended December 31,
	2012		2011		2010
	(in thousands)
2014 Notes coupon interest at a rate of 5%	$	8,625	$	8,625	$	8,625
2014 Notes amortization of discount at an additional effective interest rate of 11.7%	14,695		12,622		10,116
2010 Notes amortization of discount at an effective interest rate of 8.4%	—		—		958
Total interest expense on convertible notes	$	23,320	$	21,247	$	19,699