Equity - Common Stock (Details) - USD ($)			6 Months Ended
	Jun. 12, 2017	Apr. 17, 2015	Jun. 30, 2017	Jun. 30, 2016
Class of Stock [Line Items]
Issuance of common stock, net			$ 118,354,000	$ 174,439,000
ATM Program
Class of Stock [Line Items]
Maximum aggregate offering amount	$ 150,000,000
Common stock, shares, issued (in shares)			176,244
Common stock share price (in dollars per share)			$ 27.51
Issuance of common stock, net			$ 4,800,000
Net proceeds from issuance of common stock			4,800,000
Shares available under ATM (in shares)			$ 145,200,000
Previous ATM Program
Class of Stock [Line Items]
Maximum aggregate offering amount		$ 125,000,000
Common stock, shares, issued (in shares)			4,390,917
Common stock share price (in dollars per share)			$ 26.35
Issuance of common stock, net			$ 115,700,000
Net proceeds from issuance of common stock			$ 114,000,000