Stockholders' Equity (Deficit) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands								12 Months Ended
	Jun. 16, 2015	Nov. 05, 2014	Jun. 20, 2014	May. 27, 2014	Oct. 23, 2013	Apr. 16, 2013	Apr. 10, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 01, 2015	Jan. 01, 2014	Apr. 30, 2013	Feb. 28, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized								200,000,000	200,000,000
Common Stock, Shares, Outstanding								46,162,525	41,031,770
Common Stock, Shares, Issued								46,162,525	41,031,770
New issues of stock during period								4,341,250		8,418,000
Offering price per share								$ 39.75		$ 14.00
Stock issuance costs								$ 10,685		$ 10,218
Proceeds from public offerings, net of offering costs								$ 161,879	$ 225,938	107,634
Common Stock, Capital Shares Reserved for Future Issuance								5,882,313	4,678,696
Stock Issued During Period, Shares, Employee Stock Purchase Plans								56,583	26,275
Employees' contribution liabilities, ESPP								$ 9,721	$ 6,833
Share-based compensation, cash received from exercise of stock options								$ 3,200	$ 5,000	$ 1,900
The 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be granted							1,408,450
Share-based compensation, equity increase			4.00%					2.50%
Share-based compensation, nonvested awards, compensation not yet recognized, stock options								$ 31,600
Unrecognized compensation costs, period of recognition								2 years 10 months 11 days
Common Stock, Capital Shares Reserved for Future Issuance								1,609,791	1,147,526
The 2013 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be granted								2,816,901
The 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be granted							244,717
The 2013 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be granted														704,225
Share-based compensation, equity increase								1.00%
Number of shares authorized, increase amount								422,535
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized								410,317	266,649
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant											1,381,191	970,874
Common Stock, Capital Shares Reserved for Future Issuance								1,298,333	944,599
Share-based compensation, maximum employee subscription rate								15.00%
Discount from market price, entry date								15.00%
Discount from market price, purchase date								15.00%
Employees' contribution liabilities, ESPP								$ 500
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New issues of stock during period	4,341,250	4,197,500		8,395,000
Offering price per share	$ 39.75	$ 29.00		$ 14.22
Proceeds from public offerings, net of offering costs	$ 161,900	$ 114,000		$ 111,800
Common Stock | IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New issues of stock during period							7,320,000
Offering price per share							$ 14.00
Proceeds from initial public offering							$ 93,300
Public offering underwriting discounts and commissions							7,100
Stock issuance costs							$ 2,100
Shares converted in stock conversion							15,556,091
Warrants to purchase common stock							1,613,395						1,549,628
Common Stock | Over-allotment option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New issues of stock during period	566,250	547,500		1,095,000		1,098,000
Offering price per share						$ 14.00
Stock issuance costs						$ 1,100
Proceeds from public offerings, net of offering costs						$ 14,300
Common Stock | Secondary offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New issues of stock during period					2,476,995