Equity - At-the-Market (ATM) Program (Details) - USD ($) $ in Thousands	6 Months Ended		22 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017
At-the-market (ATM) Program
Procceds from At-the-Market (ATM) program	$ 52,442	$ 44,565
ATM
At-the-market (ATM) Program
Shares authorized	12,000,000
Share issuances, net of costs (in shares)	935,746	710,000	4,429,187
Procceds from At-the-Market (ATM) program	$ 52,400	$ 44,600	$ 255,600