Shareholders' Equity - Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	17 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Nov. 14, 2016	May 02, 2012
Equity [Abstract]
Number of shares authorized to be repurchased (in shares)			500,000.0	500,000
Number of shares repurchased (in shares)	0	52,036
Payments for repurchase of common stock		$ 0.3
Remaining number of shares authorized to be repurchased (in shares)	447,964	447,964
Average price per share of treasury stock acquired (in dollars per share)	$ 44.95
Movement in Treasury Stock [Roll Forward]
Beginning balance (in shares)	633,939
Purchases (in shares)	0	52,036
Restricted stock grants (in shares)	(77,690)
Forfeitures and other (in shares)	0
Ending balance (in shares)	556,249	556,249