Debt (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Commercial Paper and Borrowings Under Bank Credit Facilities
Balance	$ 110.8	$ 4.3
Weighted average interest rate	2.77%	1.02%
Outstanding balances of debt obligations and the applicable interest rates
Total debt principal	$ 4,473.1	$ 4,412.6
Debt discount, net	(35.9)	(36.2)
Debt adjustment for fair value hedges	(7.5)	(4.7)
Total Debt	$ 4,429.7	4,371.7
Recourse Fixed Rate Debt Secured One [Member] [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Mar. 04, 2014
Final Maturity	Jul. 30, 2019
Fixed Interest Rate	2.50%
Total Debt	$ 250.0	250.0
Recourse Fixed Rate Debt Unsecured Three [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Aug. 28, 1996
Final Maturity	Feb. 28, 2018
Fixed Interest Rate	7.86%
Total Debt	$ 0.0	11.6
Recourse Fixed Rate Debt Unsecured Four [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Oct. 31, 2014
Final Maturity	Mar. 30, 2020
Fixed Interest Rate	2.60%
Total Debt	$ 250.0	$ 250.0
Recourse Floating Rate Debt Unsecured Three [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Aug. 28, 2014
Final Maturity		Aug. 28, 2024
Floating Interest Rate	4.00%
Total Debt	$ 100.0	$ 100.0
Recourse Fixed Rate Debt Unsecured Four [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Feb. 06, 2015
Final Maturity	Mar. 30, 2020
Fixed Interest Rate	2.60%
Total Debt	$ 100.0	100.0
Recourse Fixed Rate Debt Unsecured Five [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	May 27, 2011
Final Maturity	Jun. 01, 2021
Fixed Interest Rate	4.85%
Total Debt	$ 250.0	250.0
Recourse Fixed Rate Debt Unsecured Six [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Sep. 20, 2011
Final Maturity	Jun. 01, 2021
Fixed Interest Rate	4.85%
Total Debt	$ 50.0	50.0
Recourse Fixed Rate Debt Unsecured Seven [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Jun. 11, 2012
Final Maturity	Jun. 15, 2022
Fixed Interest Rate	4.75%
Total Debt	$ 250.0	250.0
Recourse Fixed Rate Debt Unsecured Fifteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Mar. 19, 2013
Final Maturity	Mar. 30, 2023
Fixed Interest Rate	3.90%
Total Debt	$ 250.0	250.0
Recourse Fixed Rate Debt Unsecured Eight [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Nov. 05, 2018
Final Maturity	Feb. 15, 2024
Fixed Interest Rate	4.35%
Total Debt	$ 300.0	0.0
Recourse Fixed Rate Debt Unsecured Sixteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Feb. 06, 2015
Final Maturity	Mar. 30, 2025
Fixed Interest Rate	3.25%
Total Debt	$ 300.0	300.0
Recourse Fixed Rate Debt Unsecured Sixteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Sep. 13, 2016
Final Maturity	Sep. 15, 2026
Fixed Interest Rate	3.25%
Total Debt	$ 350.0	350.0
Recourse Fixed Rate Debt Unsecured Sixteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Feb. 09, 2017
Final Maturity	Mar. 30, 2027
Fixed Interest Rate	3.85%
Total Debt	$ 300.0	300.0
Recourse Fixed Rate Debt Unsecured Seventeen [Member] [Domain]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Nov. 02, 2017
Final Maturity	Mar. 15, 2028
Fixed Interest Rate	3.50%
Total Debt	$ 300.0	300.0
Recourse Fixed Rate Debt Unsecured Thirteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	May 07, 2018
Final Maturity	Nov. 07, 2028
Fixed Interest Rate	4.55%
Total Debt	$ 300.0	0.0
Recourse Fixed Rate Debt Unsecured Eighteen [Member] [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Mar. 04, 2014
Final Maturity	Mar. 15, 2044
Fixed Interest Rate	5.20%
Total Debt	$ 300.0	300.0
Recourse Fixed Rate Debt Unsecured Fifteen [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Feb. 06, 2015
Final Maturity	Mar. 30, 2045
Fixed Interest Rate	4.50%
Total Debt	$ 250.0	250.0
Recourse Fixed Rate Debt Unsecured Twenty [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	May 16, 2016
Final Maturity	May 30, 2066
Fixed Interest Rate	5.63%
Total Debt	$ 150.0	150.0
Recourse Fixed Rate Debt Unsecured Seventeen [Member] [Domain]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Nov. 19, 2013
Final Maturity	Mar. 15, 2019
Fixed Interest Rate	2.50%
Total Debt	$ 0.0	300.0
Recourse Fixed Rate Debt Unsecured Eighteen [Member] [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Jan. 30, 2015
Final Maturity	Dec. 31, 2018
Fixed Interest Rate	1.20%
Total Debt	$ 0.0	60.0
Recourse Fixed Rate Debt Unsecured Twenty [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Nov. 29, 2010
Final Maturity	Nov. 30, 2018
Fixed Interest Rate	3.70%
Total Debt	$ 0.0	3.0
Recourse Fixed Rate Debt Unsecured Twenty One [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Dec. 27, 2010
Final Maturity	Oct. 31, 2018
Fixed Interest Rate	3.84%
Total Debt	$ 0.0	12.0
Recourse Fixed Rate Debt Unsecured Twenty Two [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Mar. 19, 2013
Final Maturity	Jul. 30, 2018
Fixed Interest Rate	2.38%
Total Debt	$ 0.0	250.0
Recourse Fixed Rate Debt [Member]
Outstanding balances of debt obligations and the applicable interest rates
Total Debt	$ 3,950.0	$ 3,986.6
Recourse Floating Rate Debt Unsecured Five [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Nov. 06, 2017
Final Maturity		Nov. 05, 2021
Floating Interest Rate	3.30%
Total debt principal	$ 300.0	$ 200.0
Recourse Floating Rate Debt Secured Two [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Dec. 22, 2016
Final Maturity		Dec. 20, 2021
Floating Interest Rate	0.85%
Total debt principal	$ 63.1	$ 66.0
Recourse Floating Rate Debt Unsecured Four [Member]
Outstanding balances of debt obligations and the applicable interest rates
Date of Issue	Sep. 23, 2015
Final Maturity		Sep. 23, 2025
Floating Interest Rate	4.07%
Total Debt	$ 60.0	$ 60.0
Total Recourse Floating Rate Debt [Member]
Outstanding balances of debt obligations and the applicable interest rates
Total Debt	523.1	$ 426.0
Line of Credit US [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600.0
Line of Credit Facility, Capacity Available for Trade Purchases	$ 500.0

Debt adjustment for fair value hedges .

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Date the debt instrument was issued, in CCYY-MM-DD format.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount, after accumulated amortization, of debt discount (premium).

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The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date for financing purchases of goods acquired for inventory or imminent delivery to a customer.

+ References

No definition available.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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Amount of borrowings classified as other, maturing within one year or the normal operating cycle, if longer.

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