FAIR VALUE MEASUREMENTS (Details) (Recurring basis, USD $)	Mar. 31, 2015
Carrying Amount
Assets:
United States treasury bills	$ 329,990,000
Marketable equity securities	5,619,000
Liabilities:
Debt	396,484,000
Amount of equity component of convertible notes	77,000,000
Fair Value
Assets:
United States treasury bills	329,990,000
Marketable equity securities	5,619,000
Total assets	335,609,000
Liabilities:
Debt	380,175,000
Total liabilities	380,175,000
Level 1
Assets:
United States treasury bills	329,990,000
Marketable equity securities	5,619,000
Total assets	335,609,000
Liabilities:
Debt	380,175,000
Total liabilities	$ 380,175,000