Fair Value Measurements (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Description	The Company did not have material transfers between Levels 1 and 2 for either financial assets or liabilities during the years ended December 31, 2016 and 2015.
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0
Issuance of convertible notes	200,000,000
2010 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt	302,600,000	$ 305,600,000
Convertible Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	228,400,000
Convertible Notes [Member] | Liability Component [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Issuance of convertible notes	$ 153,200,000