COMMITMENTS AND CONTINGENCIES (Details) (USD $) In Thousands, unless otherwise specified		1 Months Ended					0 Months Ended
	Sep. 30, 2013	Jun. 30, 2009 4.375% convertible notes due 2014	Sep. 30, 2013 4.375% convertible notes due 2014	Aug. 31, 2013 4.375% convertible notes due 2014	Jun. 12, 2013 4.375% convertible notes due 2014	Mar. 31, 2013 4.375% convertible notes due 2014	Jul. 17, 2013 1.00% Convertible Notes due 2018	Sep. 30, 2013 1.00% Convertible Notes due 2018	Jun. 18, 2013 1.00% Convertible Notes due 2018
Commitments and contingencies
Interest rate on convertible notes (as a percent)		4.375%	4.375%	4.375%				1.00%	1.00%
Amount pertaining to exercise of over-allotment of debt by underwriters		$ 18,000					$ 37,500
Aggregate principal amount		138,000							250,000
Expenditures due upon deferred revenue recognition	393,723
Interest
2014 (remaining six months)								1,541
2015								2,875
2016								2,875
2017								2,875
2018								2,875
Thereafter								1,438
Total								14,479
1.00% Convertible Notes
Thereafter								287,500
Total					138,000	138,000		287,500
Annual commitments
2014 (remaining six months)								1,541
2015								2,875
2016								2,875
2017								2,875
2018								2,875
Thereafter								288,938
Total								$ 301,979