Debt and Financing (Details) $ in Millions	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,150.0
Unaccreted discount and debt issuance costs	(15.6)
Long-term Debt	$ 2,134.4
Redemption percent due to change in control	101.00%
Fixed Rate Note Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 350.0
Effective Interest Rates	3.36%
Long-term debt, stated interest rate	3.125%
Fixed rate note due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300.0
Effective Interest Rates	3.47%
Long-term debt, stated interest rate	3.30%
Fixed rate note due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300.0
Effective Interest Rates	4.69%
Long-term debt, stated interest rate	4.60%
Fixed Rate Note Due 2024, Issued March 2014 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 350.0
Effective Interest Rates	4.63%
Long-term debt, stated interest rate	4.50%
Fixed Rate Note Due 2024, Issued February 2016 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 150.0
Effective Interest Rates	4.87%
Long-term debt, stated interest rate	4.50%
Fixed rate note due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300.0
Effective Interest Rates	4.47%
Long-term debt, stated interest rate	4.35%
Fixed rate note due 2041 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 400.0
Effective Interest Rates	6.03%
Long-term debt, stated interest rate	5.95%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	$ 0.0

Repurchase Price Percentage Related to Change of Control

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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- Definition

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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Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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