Financing Arrangements - underwritten public offering (Details) $ / shares in Units, $ in Millions	1 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Financing Arrangements
Underwritten public offering (in shares) | shares	3,795,000
Offered price (per share) | $ / shares	$ 60.00
Net Proceeds from public offering	$ 215.8
Underwriting discounts and commissions and offering expenses	$ 11.9