Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 10, 2017	Aug. 11, 2016	Apr. 25, 2016
Class of Stock [Line Items]
Common stock, shares authorized		240,000,000	240,000,000
Preferred stock, shares authorized		5,000,000
Preferred stock, par value per share (in dollars per share)		$ 0.01
Net proceeds from issuance of common stock		$ 96,547	$ 0	$ 0
April ATM Program [Member]
Class of Stock [Line Items]
Maximum value of common stock to be issued							$ 50,000
Value of common stock issued		50,000
Net proceeds from issuance of common stock		47,700
Payments for commissions		$ 1,300
April ATM Program [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares issued		6,309,355
Price per share issued (in dollars per share)		$ 7.92
August ATM Program [Member]
Class of Stock [Line Items]
Maximum value of common stock to be issued						$ 50,000
Value of common stock issued		$ 50,000
Net proceeds from issuance of common stock		48,800
Payments for commissions		$ 1,000
August ATM Program [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares issued		6,709,377
Price per share issued (in dollars per share)		$ 7.45
Underwritten Public Equity Offering [Member] | Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Shares issued					26,450,000
Price per share issued (in dollars per share)					$ 8.65
Net proceeds from issuance of common stock	$ 220,000