Financing Arrangements - Underwritten Public Offering (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Financing Arrangements
Stock issued under equity offering, net (in shares) | shares	3,795,000	3,795,000
Stock offering price (per share) | $ / shares	$ 60.00	$ 60.00
Proceeds from equity offering, net	$ 215,800	$ 215,832
Underwriting discounts and commissions and offering expenses	$ 11,900