Equity Offering (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Class of Stock [Line Items]
Proceeds from issuance of common stock	$ 398,600	$ 399,272	$ 23,053
Common Stock
Class of Stock [Line Items]
Shares issued	5,700,000	5,700,000