Income Taxes - Components of deferred tax liabilities and assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax liabilities:
Depreciation, depletion, and amortization	$ 718.4	$ 578.9
Partially-owned subsidiaries basis difference	131.7	117.2
Convertible debt	0.0	91.4
Total deferred tax liabilities	850.1	787.5
Deferred tax assets:
Workers compensation, pensions, and other benefits	5.7	6.6
Warranties and reserves	8.1	5.8
Equity items	34.0	31.9
Tax loss carryforwards and credits	65.5	24.8
Inventory	8.9	7.2
Accrued liabilities and other	9.1	8.1
Total deferred tax assets	131.3	84.4
Net deferred tax liabilities before valuation allowances	718.8	703.1
Valuation allowances	15.1	7.8
Net deferred tax liabilities before reserve for uncertain tax positions	733.9	710.9
Deferred tax assets included in reserve for uncertain tax positions	(2.3)	(1.9)
Adjusted net deferred tax liabilities	$ 731.6	$ 709.0