Shareholders' Equity Shareholders' Equity Note (Detail textual) (Details) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) shares
Stockholders Equity Note [Line Items]
Stock Repurchased During Period, Shares	1.7
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	15.0
Accelerated share repurchase program [Member]
Stockholders Equity Note [Line Items]
Stock Repurchased During Period, Shares	0.8
Stock Repurchase Program, Authorized Amount | $	$ 50.0