Redemption of Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Apr. 30, 2017	Sep. 30, 2017
Redemption of Preferred Stock
Excess of redemption value over carrying value of preferred shares subject to redemption		$ 13,373
Class F Preferred Stock
Redemption of Preferred Stock
Preferred stock redeemed (in shares)	16,350,000
Preferred stock, dividend rate (as a percent)	6.625%
Preferred stock, redemption price per share (in dollars per share)	$ 25
Excess of redemption value over carrying value of preferred shares subject to redemption		$ 13,400