Debt and Finance Leases - 5.50% Senior Notes Due 2024 - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 22, 2014
Debt Instrument [Line Items]
Gain on debt extinguishment		$ 0	$ 786,000	$ 0
Senior Notes | Senior Notes due 2024 at a fixed interest rate of 5.50%
Debt Instrument [Line Items]
Face amount					$ 550,000,000
Interest rate		5.50%			5.50%
Debt repurchased	$ 11,000,000		11,000,000
Debt retired	10,000,000		$ 10,000,000
Gain on debt extinguishment	$ 1,000,000