Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended
	Jul. 31, 2015	Mar. 31, 2015	Mar. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2012	Jan. 25, 2016
Subsidiary, Sale of Stock [Line Items]
Sales per share price range								$ 5.56
Proceeds from Issuance of Common Stock				$ 0	$ 197,093
Sale of Stock, Price Per Share								$ 5.56
Convertible Debt [Member]
Subsidiary, Sale of Stock [Line Items]
Adjustments to Additional Paid IN capital, Cost and Expenses on Derivative Transaction			$ 38,500
Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Sales per share price range		$ 7.25
Shares sold		27,758,620
Common stock issued upon exercise in full over-allotment granted		3,620,689
Proceeds from shares sold		$ 190,000
Offering costs		11,600
Stock Issued During Period, Value, New Issues		$ 190,000
Stock Issued During Period, Shares, New Issues		27,758,620
Sale of Stock, Price Per Share		$ 7.25
2012 Sales Agreement [Member]
Subsidiary, Sale of Stock [Line Items]
Sales per share price range	$ 11.53					$ 10.01
Shares sold	600,000					800,000
Proceeds from shares sold	$ 6,600					$ 8,000
Proceeds from Issuance of Common Stock	700
Stock Issued During Period, Value, New Issues	$ 6,600					$ 8,000
Stock Issued During Period, Shares, New Issues	600,000					800,000
Sale of Stock, Price Per Share	$ 11.53					$ 10.01
Maximum [Member] | 2012 Sales Agreement [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock authorized for issuance under prior shelf registration statement with SEC, dollar amount							$ 50,000