Shareholders' Equity - Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Nov. 14, 2016	May 02, 2012
Class of Stock [Line Items]
Remaining number of shares authorized to be repurchased (in shares)	500,000
Purchases (in shares)	24,086	38,245
Purchase of treasury stock	$ 0.2	$ 1.7
Average price per share of treasury stock acquired and held (dollars per share)	$ 38.13
May 2, 2012 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased (in shares)				500,000.0
November 14, 2016 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased (in shares)			500,000.0