Shareholders' Equity - Summary of Stock Appreciation Rights (Details) - SARS - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Nov. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock, Outstanding, Beginning Balance (in shares)		1,000,000
Stock, Granted (in shares)	0	400,000	0
Stock, Exercised (in shares)		(300,000)
Stock, Canceled (in shares)		(100,000)
Stock, Outstanding, Ending Balance (in shares)		1,000,000
Stock, Exercisable (in shares)		200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Beginning Balance (in USD per share)		$ 11.52
Weighted Average Exercise Price, Granted (in USD per share)		22.35
Weighted Average Exercise Price, Exercised (in USD per share)		6.97
Weighted Average Exercise Price, Canceled (in USD per share)		17.21
Weighted Average Exercise Price, Ending Balance (in USD per share)		16.62
Weighted Average Exercise Price, Exercisable (in USD per share)		$ 8.17
Weighted Average Remaining Contractual Life, Outstanding		4 years 8 months 12 days
Weighted Average Remaining Contractual Life, Exercisable		1 year 2 months 12 days
Aggregate Intrinsic Value, Outstanding		$ 14.6
Aggregate Intrinsic Value, Exercisable		$ 5.4