Fair Value Measurement - (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		$ 51,115
Level 1
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		499
Level 2
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		60,477
Level 3
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		(9,861)
Commercial paper
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		22,872
Commercial paper | Level 1
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Commercial paper | Level 2
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		22,872
Commercial paper | Level 3
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Corporate bonds
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		28,060
Corporate bonds | Level 1
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Corporate bonds | Level 2
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		28,060
Corporate bonds | Level 3
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Commodity derivatives
Assets (liabilities) measured at fair value
Assets (liabilities), fair value	$ (3,116)	10,044
Commodity derivatives | Level 1
Assets (liabilities) measured at fair value
Assets (liabilities), fair value	(84)	499
Commodity derivatives | Level 2
Assets (liabilities) measured at fair value
Assets (liabilities), fair value	(3,032)	9,545
Commodity derivatives | Level 3
Assets (liabilities) measured at fair value
Assets (liabilities), fair value	$ 0	0
Contingent consideration for acquisitions
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		(9,861)
Contingent consideration for acquisitions | Level 1
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Contingent consideration for acquisitions | Level 2
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		0
Contingent consideration for acquisitions | Level 3
Assets (liabilities) measured at fair value
Assets (liabilities), fair value		$ (9,861)