Equity - At-the-Market (ATM) Program (Details) - USD ($) $ in Thousands	9 Months Ended		25 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
At-the-market (ATM) Program
Procceds from At-the-Market (ATM) program	$ 487,998	$ 85,780
ATM
At-the-market (ATM) Program
Share issuances, net of costs (in shares)	8,506,559	1,312,269	12,000,000
Procceds from At-the-Market (ATM) program	$ 488,000	$ 85,800	$ 691,100