Balance Sheet Account Detail (Fair Value Measurements) (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 207,900	$ 84,500
Government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	124,553	26,798
Contingently issuable common stock	14,700	14,600
Government securities | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	124,553	26,798
Contingently issuable common stock	0	0
Government securities | Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Contingently issuable common stock	0	0
Government securities | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Contingently issuable common stock	$ 14,700	$ 14,600