Equity (Details) - USD ($) $ in Thousands					12 Months Ended
	May 17, 2018	Oct. 10, 2017	Dec. 09, 2016	Mar. 11, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 01, 2017	May 31, 2017
Subsidiary, Sale of Stock [Line Items]
Offering costs	$ 200	$ 300			$ 204	$ 280	$ 847
Repayment of debt					$ 45,000
Consideration received on sale of stock			$ 145,800	$ 141,500
Common stock, shares authorized (in shares)					160,000,000	160,000,000
Issuance cost of equity			$ 400	$ 800	$ 204	$ 280	$ 1,190
Preferred shares authorized (in shares)					2,000,000
Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)			6,000,000	7,500,000
Common stock, shares authorized (in shares)								160,000,000	120,000,000
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Consideration received on sale of stock	$ 226,400	$ 208,400
Public Stock Offering | Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)	7,000,000	8,000,000