Equity - At-the-Market (ATM) Program (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended		16 Months Ended
	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Procceds from At-the-Market (ATM) program		$ 166,781	$ 36,348
ATM
Shares authorized	12,000,000
Share issuances, net of costs (in shares)		2,779,140	714,301	3,493,441
Procceds from At-the-Market (ATM) program		$ 166,800	$ 36,300	$ 203,100