Stockholders' Equity (ATM Program) (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Total allowable shares (in shares)	375,000,000		375,000,000
Total shares issued (in shares)	173,407,606		171,694,209
Net proceeds	$ 54,084	$ 87,978
Stock issuance costs	$ 7,809	$ 115
ATM
Class of Stock [Line Items]
Total allowable shares (in shares)	12,000,000
Total shares issued (in shares)	11,140,162
Shares of common stock (in shares)	1,417,977	1,495,548
Average price per share (net) (in dollars per share)	$ 36.68	$ 53.52
Net proceeds	$ 52,018	$ 80,046
Stock issuance costs	$ 746	$ 766