Stockholders' Equity (Details)					12 Months Ended			26 Months Ended
	Sep. 15, 2016 USD ($) $ / shares shares	Nov. 03, 2014 USD ($)	Sep. 30, 2014 USD ($)	Oct. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) vote	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) shares
Class of Stock [Line Items]
Common stock initial public offering (in shares) | shares				7,728,000
Common stock, offering price per share (in dollars per share) | $ / shares				$ 10.00
Net proceeds from initial public offering				$ 68,300,000
Proceeds from convertible debt					$ 0	$ 0	$ 122,853,000
Shelf registration statement, aggregate dollar amount						0
Proceeds from sale of common stock					$ 168,479,000	$ 50,451,000	$ 0
Number of voting rights | vote					1
Maximum
Class of Stock [Line Items]
Shelf registration statement, aggregate dollar amount		$ 150,000,000.0
Cantor Fitzgerald and Co. | Common Stock
Class of Stock [Line Items]
Common stock issued and sold under sales agreement (in shares) | shares								5,933,712
Proceeds from sale of common stock	$ 71,000,000							$ 146,600,000
Sale of stock, commissions, percentage of gross sales (up to)								3.00%
New shares issued under shelf registration (in shares) | shares	2,542,373
Price per share issued under underwriting agreement (in dollars per share) | $ / shares	$ 29.50
Underwriting discounts, fees and expenses	$ 4,000,000
RBC Capital Markets LLC and Cantor Fitzgerald and Co | Common Stock
Class of Stock [Line Items]
Shelf registration statement, aggregate dollar amount								$ 96,200,000
Common stock issued and sold under sales agreement (in shares) | shares								4,179,156
Convertible debt
Class of Stock [Line Items]
Proceeds from convertible debt			$ 122,900,000