Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Total carrying value at period end
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - restricted	$ 33,661
Derivative liabilities	(1,944)
Total	31,717
Quoted prices in active markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - restricted	33,661
Derivative liabilities	0
Total	33,661
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - restricted	0
Derivative liabilities	(1,944)
Total	(1,944)
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - restricted	0
Derivative liabilities	0
Total	$ 0