Equity - Dividend Reinvestment and Stock Purchase Plan (Details) - USD ($) $ in Millions	9 Months Ended		67 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016
Equity
Authorized common shares to be issued	26,000,000
Number of common shares issued	133,432	7,565,432	12,833,294
Amount raised from shares issued	$ 8.2	$ 360.9	$ 589.8
Number of common shares issued under the waiver approval process		7,413,207
Amount raised from share issued under the waiver approval process		$ 353.7