Investments	12 Months Ended
Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The Company did not have any investment securities related to certificates of deposit as of December 31, 2016. The Company had investment securities related to certificates of deposit in the amount of $0.3 million as of December 31, 2015. No unrealized gains or losses were recorded as of December 31, 2015 related to these investment securities. In November 2014, the Company acquired an 8% ownership interest in the common stock of Highview, a London, England based developmental stage company specializing in power storage, for $2.8 million in cash (the "Highview Investment"). The Company evaluated the Highview Investment and determined that it should account for it under the cost method. As of December 31, 2016 and December 31, 2015, the Highview Investment was in the amount of $1.0 million and $2.8 million, respectively. No unrealized gains or losses were recorded as of December 31, 2016 and December 31, 2015 related to the Highview Investment. The Highview Investment is evaluated for impairment based on indicators of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. When there are no indicators of impairment present, the Company estimates the fair value of the Highview Investment only if it is practical to do so. As of December 31, 2016, the Company estimated the fair value of the Highview Investment based upon an anticipated equity raise by Highview at a price of £2.00 per share. As £2.00 per share is less than the Company's cost per share of £4.25, the Company recorded an impairment charge of $1.8 million as of December 31, 2016, which is included in Other line item in the Consolidated Statement of Operations. As of December 31, 2015, there were no indicators of impairment, and the Company estimated that the fair value of the Highview Investment approximated the November 2014 purchase price due to the proximity of the purchase date to December 31, 2015.

Investments

The Company did not have any investment securities related to certificates of deposit as of December 31, 2016. The Company had investment securities related to certificates of deposit in the amount of $0.3 million as of December 31, 2015. No unrealized gains or losses were recorded as of December 31, 2015 related to these investment securities.

In November 2014, the Company acquired an 8% ownership interest in the common stock of Highview, a London, England based developmental stage company specializing in power storage, for $2.8 million in cash (the "Highview Investment"). The Company evaluated the Highview Investment and determined that it should account for it under the cost method. As of December 31, 2016 and December 31, 2015, the Highview Investment was in the amount of $1.0 million and $2.8 million, respectively. No unrealized gains or losses were recorded as of December 31, 2016 and December 31, 2015 related to the Highview Investment.

The Highview Investment is evaluated for impairment based on indicators of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. When there are no indicators of impairment present, the Company estimates the fair value of the Highview Investment only if it is practical to do so. As of December 31, 2016, the Company estimated the fair value of the Highview Investment based upon an anticipated equity raise by Highview at a price of £2.00 per share. As £2.00 per share is less than the Company's cost per share of £4.25, the Company recorded an impairment charge of $1.8 million as of December 31, 2016, which is included in Other line item in the Consolidated Statement of Operations. As of December 31, 2015, there were no indicators of impairment, and the Company estimated that the fair value of the Highview Investment approximated the November 2014 purchase price due to the proximity of the purchase date to December 31, 2015.