Equity - Schedule of ATM Program Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Class of Stock [Line Items]
Remaining offering amount available	$ 236,100		$ 236,100
Gross proceeds			170,485	$ 105,889
Maximum [Member]
Class of Stock [Line Items]
Authorized aggregate offering price of common stock	$ 300,000		$ 300,000
At-The-Market Offering [Member]
Class of Stock [Line Items]
Number of shares (in shares)	3,399	7,175	10,574
Average sales price per share (in usd per share)	$ 18.82	$ 15.31	$ 16.43
Gross proceeds	$ 63,947	$ 109,813	$ 173,760