Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Schedule of shares purchased under the respective stock purchase plans

The following table shows shares purchased and value ($ in millions) under the respective stock purchase plans:

	Three Months Ended March 31,
	2018			2017
	Shares	Amount		Shares	Amount
2018 Stock Purchase Plan	66,724	$	5.3	—	$	—
2017 Stock Purchase Plan	—	—		—	—
2016 Stock Purchase Plan	—	—		85,354	6.8