v3.10.0.1

Leases (Investment in Direct Financing Lease) (Details) $ in Millions	Dec. 31, 2018 USD ($) mi	Dec. 31, 2017 USD ($)
Direct Financing Lease [Line Items]
Direct Financing Lease, Minimum Payments to be Received	$ 17.5	$ 19.2
Direct Financing Lease, Unearned Income	3.5	4.1
Direct Financing Lease, Net Investment	14.0	15.1
Direct Financing Leases, Future Minimum Payments Receivable, Next Twelve Months	1.7
Direct Financing Leases, Future Minimum Payments, Receivable in Two Years		1.7
Direct Financing Leases, Future Minimum Payments Due in Three Years		1.7
Direct Financing Leases, Future Minimum Payments, Receivable in Four Years		1.7
Direct Financing Leases, Future Minimum Payments Due in Five Years		1.7
Other Current Assets [Member]
Direct Financing Lease [Line Items]
Direct Financing Lease, Net Investment	1.1	1.1
Other Noncurrent Assets [Member]
Direct Financing Lease [Line Items]
Direct Financing Lease, Net Investment	$ 12.9	$ 14.0
Texas and New Mexico Pipeline (Leased) [Member]
Direct Financing Lease [Line Items]
Pipeline, Length | mi	40

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Amount of minimum lease payments for capital leases due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for capital leases due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments to be received by the lessor for capital leases in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments to be received by the lessor for capital leases in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments to be received by the lessor for capital leases in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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The net investment in direct financing leases as of the balance sheet date consisting of: (a) minimum lease payments due on direct financing leases, (b) unguaranteed residual value, and (c) any unamortized initial direct costs; less: (i) executory costs, (ii) unearned income, and (iii) the accumulated allowance for uncollectible minimum lease payments.

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The remaining (unamortized) difference between the gross investment in a direct financing lease and the cost or carrying amount, if different, of the leased property as of the balance sheet date.

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Amount of remaining payments as of the balance sheet date that lessees are obligated to make or can be required to make under direct financing leases, including any guarantee of residual value and executory costs. The amount also includes any guaranteed rental payments by an unrelated third-party provided that are financially capable of making such payments.

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