Senior convertible notes (Tables)

12 Months Ended

Dec. 31, 2012

Summary of Senior Convertible Notes

Senior convertible notes consist of the following (in thousands):

	December 31,
	2011			2012
2013 notes
Principal amount	$	115,000		$	115,000
Unaccreted debt issuance expense		(1,140	)		(557	)
Net carrying amount		113,860			114,443
2015 notes
Principal amount	$	100,000		$	100,000
Unaccreted debt issuance expense		(3,218	)		(2,417	)
Net carrying amount		96,782			97,583
Senior convertible notes	$	210,642		$	212,026