Equity - Common Stock (Details) - USD ($)				9 Months Ended
	Sep. 21, 2017	Jun. 12, 2017	Apr. 17, 2015	Sep. 30, 2017	Sep. 30, 2016
Class of Stock [Line Items]
Shares, Issued				11,043,880
Common stock share price (in dollars per share)				$ 27.99
Issuance of common stock, net				$ 303,868,000	$ 174,302,000
Net proceeds from issuance of common stock				304,500,000
At-The-Market Equity Offering Program $300M
Class of Stock [Line Items]
Maximum aggregate offering amount	$ 300,000,000
Issuance of common stock, net				309,100,000
ATM Program
Class of Stock [Line Items]
Maximum aggregate offering amount		$ 150,000,000
Shares available under ATM (in shares)				$ 256,600,000
Previous ATM Program
Class of Stock [Line Items]
Maximum aggregate offering amount			$ 125,000,000