Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 20, 2017
Equity [Abstract]
Shares authorized for repurchase		100,000,000
Shares repurchased during period (in shares)	99,000
Weighted average cost per share (in dollars per share)	$ 66.28
Authorized amount remaining for repurchase	$ 93.4