Business Combinations - Acquisition of Cloverleaf (Details) $ in Thousands	May 01, 2019 USD ($) expansion_opportunity	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Assets
Goodwill		$ 310,640	$ 186,095
Cloverleaf
Business Acquisition [Line Items]
Fair value of assets and liabilities acquired	$ 1,240,000
Assets
Land	60,834
Building and improvements	673,371
Machinery and equipment	135,941
Assets under construction	19,977
Operating lease right-of-use assets	1,254
Cash and cash equivalents	4,332
Restricted cash	526
Accounts receivable	21,492
Goodwill	117,650
Acquired identifiable intangibles:
Other assets	6,942
Total assets	1,300,872
Liabilities
Accounts payable and accrued expenses	39,978
Notes payable	3,878
Operating lease obligations	1,254
Unearned revenue	3,536
Pension and postretirement benefits	859
Deferred tax liability	8,488
Total liabilities	57,993
Total consideration	$ 1,242,879
Number of expansion opportunities | expansion_opportunity	3
Deferred tax liability, intangible assets	$ 1,000
Customer relationships | Cloverleaf
Acquired identifiable intangibles:
Identifiable intangibles	$ 256,927
Liabilities
Weighted average remaining intangible amortization life (in months)	25 years
Trade names and trademarks | Cloverleaf
Acquired identifiable intangibles:
Identifiable intangibles	$ 1,626
Liabilities
Weighted average remaining intangible amortization life (in months)	1 year 6 months