Public Offering (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Dec. 15, 2015	Dec. 09, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 28, 2014	Apr. 07, 2014
Class of Stock [Line Items]
Public offering price (dollars per share)		$ 17	$ 20.75			$ 17.54	$ 17.64
Lock-up agreement (period)		90 days
Underwriting discount and commission fees (dollars per share)		$ 1.19
Gross proceeds from sale of common stock	$ 109,300
Stock issuance costs	5,900		$ 814	$ 0	$ 0
Proceeds from common stock issuance	$ 103,400
Common stock
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)	6,400,000			6,426,000	2,678,000
Common stock | Affiliated entity
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)		2,900,000
Public offering | Common stock
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)		5,600,000
Underwriters | Common stock
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)		838,000
Offering exempt from underwriter commission | Common stock | Affiliated entity
Class of Stock [Line Items]
Issuance of common stock and warrants (shares)		2,400,000