Shareholders’ Equity (Narrative) (Details)					1 Months Ended							3 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2014 shares	Jan. 25, 2014 USD ($) shares	Jan. 14, 2014	Sep. 24, 2013 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Aug. 31, 2015 USD ($) shares	Apr. 30, 2015 shares	Feb. 28, 2015 shares	Dec. 31, 2014 USD ($) party $ / shares shares	Jul. 31, 2014 USD ($) $ / shares shares	Sep. 30, 2013	Sep. 30, 2014 shares	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2013 shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Jul. 31, 2015 shares	Aug. 31, 2014 shares	Jan. 02, 2014 shares	Dec. 31, 2012 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reverse stock split ratio			0.02
Common stock, shares authorized									100,000,000	12,000,000,000					100,000,000	100,000,000			100,000,000
Preferred stock, shares authorized															8,000,000
Preferred stock, par value (usd per share) | $ / shares															$ 0.0001
Weighted-average grant date fair values of stock options granted | $ / shares															$ 22.56	$ 9.67	$ 6.00
Unamortized share-based compensation expense | $															$ 38,304,000
Recognized weighted average period															3 years 4 months 30 days
Stock options exercised															51,814	0
Intrinsic value of stock options exercised | $													$ 928,000
Warrants granted to purchase common stock									51,000
Warrants issued, number of third party recipients | party									2
Third party share-based compensation expense | $															$ 1,086,000	$ 63,000
Share-based compensation expense | $															13,072,000	9,080,000	$ 12,373,000
Stock issued during period, value | $															104,596,000	53,063,000	6,750,000
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $															4,084,000	1,269,000	992,000
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $															$ 8,988,000	$ 7,811,000	$ 11,381,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued						4,000
Number of shares of unvested stock awards									1,279,007						1,072,899	1,279,007	1,746,853				0
Stock issued during period, value | $						$ 92,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	39,811											7,318
Restricted Stock [Member] | Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized weighted average period															1 month
Share-based compensation expense | $															$ 1,600,000	$ 1,009,000	$ 94,000
Unamortized share-based compensation expense | $															$ 30,000
Restricted Stock [Member] | General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized weighted average period															14 months
Share-based compensation expense | $															$ 4,265,000	$ 6,856,000	$ 4,516,000
Unamortized share-based compensation expense | $															$ 2,570,000
Grant One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant vesting period									4 years
Consultant [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued		2,976
Stock issued during period, value | $		$ 25,000
Chief Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of unvested stock awards																		1,042,680
One-year Anniversary Date of Grant [Member] | Grant One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant vesting rights percentage									25.00%
One-year Anniversary Date of Grant [Member] | Grant Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant vesting rights percentage									100.00%
2013 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity plan, term											10 years
Period of share-based payment awards											4 years
Automatic annual increase based on outstanding shares of Common Stock as of the last day of the previous year end, percent											10.00%
Shares available for grant															786,525					440,441
Shares of common stock authorized for issuance					3,100,000								3,100,000						1,100,000
Shares of common stock for future issuance															3,045,210
2013 Equity Plan [Member] | Consultant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of share-based payment awards								3 years
Stock options granted								60,000
Share-based compensation expense | $															$ 362,000
2013 Equity Plan [Member] | Consultant [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted						50,000
Share-based compensation expense | $															$ 72,000
2013 Equity Plan [Member] | Chief Financial Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted							60,000
2013 Equity Plan [Member] | One-year Anniversary Date of Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage											25.00%
2013 Equity Plan [Member] | One-year Anniversary Date of Grant [Member] | Chief Financial Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage							25.00%
2013 Equity Plan [Member] | Upon Grant [Member] | Consultant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage								25.00%
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued															2,933,000	5,395,000	1,929,000
Stock options exercised															45,000
Stock issued during period, value | $																$ 1,000	$ 2,000
Common Stock [Member] | Director [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued														79,622
Common Stock [Member] | Chief Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued														1,327,048
Common Stock [Member] | Employees [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued														336,185
Series C-1 Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized									11,000						11,000	11,000
Preferred stock, par value (usd per share) | $ / shares									$ 0.0001						$ 0.0001	$ 0.0001
Shares issued upon conversion, per share															1,724
Preferred stock, shares issued									3,917						3,906	3,917
Shares reserved for future issuance									6,752,908						6,735,378	6,752,908
Liquidation preference per share | $ / shares															$ 1,000
Liquidation preference | $									$ 3,917,000						$ 3,906,000	$ 3,917,000
Conversion of Stock, Shares Issued				557
Series C-1 Convertible Preferred Stock [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued															19,134	5,341,670
Series F Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized									10,000						10,000	10,000
Preferred stock, par value (usd per share) | $ / shares									$ 0.0001						$ 0.0001	$ 0.0001
Shares issued upon conversion, per share															286
Preferred stock, shares issued									2,798						2,737	2,798
Shares reserved for future issuance									800,228						782,032	800,228
Liquidation preference | $									$ 2,798,000						$ 2,737,000	$ 2,798,000
Stock issued during period, value | $																	$ 3,250,000
Series F Preferred Stock [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued															17,360	129,105
Series C Two Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of Stock, Shares Converted				557
Underwriting Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock to be issued and sold in underwriting agreement					2,932,500					5,395,000
Proceeds from the underwriting agreement, including additional shares sold, gross | $					$ 111,400,000					$ 56,600,000
Proceeds from the underwriting agreement, including additional shares sold, net of cost | $					104,600,000					53,100,000
Issuance costs | $					$ 6,800,000					$ 3,500,000
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price per share of shares sold (usd per share) | $ / shares					$ 38					$ 10.50			$ 38
Private Placement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from Issuance or Sale of Equity | $				$ 10,000,000
Payments of Stock Issuance Costs | $				$ 300,000
Private Placement [Member] | Series F Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Securities Purchase Agreement, Number Of Shares Issued In Transaction				3,250
Securities Purchase Agreement, Price Per Share | $ / shares				$ 1,000
Private Placement [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Securities Purchase Agreement, Consideration Received Per Transaction | $				$ 10,000,000.0
Securities Purchase Agreement, Number Of Shares Issued In Transaction				1,928,620
Securities Purchase Agreement, Price Per Share | $ / shares				$ 3.50