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

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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.

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No definition available.

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- Definition

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

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Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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- Definition

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

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- Definition

Amount, after accumulated amortization, of debt issuance costs classified as current. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Parent Company Debt Schedule (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument
Long-term Debt, Excluding Current Maturities		$ 2,999.4		$ 2,449.4
Debt Instrument, Unamortized Premium (Discount), Net		9.8		(3.8)
Debt Issuance Costs, Noncurrent, Net		(28.4)		(25.7)
Current Maturities of Long-term Debt		0.0		352.0
Debt Issuance Costs, Current, Net		0.0		(0.4)
Long-term Debt		2,999.4		2,801.4
Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities		(3.1)		(2.7)
Current Maturities of Long-term Debt		0.0		2.4
Parent Company
Debt Instrument
Long-term Debt, Excluding Current Maturities		2,735.9		2,125.4
Debt Instrument, Unamortized Premium (Discount), Net		9.8		(3.8)
Debt Issuance Costs, Noncurrent, Net		(28.4)		(25.7)
Current Maturities of Long-term Debt		0.0		352.0
Debt Issuance Costs, Current, Net		0.0		(0.4)
Long-term Debt		2,735.9		2,477.4
Parent Company \| Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities		(3.1)		(2.7)
Current Maturities of Long-term Debt		0.0		2.4
Notes Issued in 1998 with 2018 Maturity Date \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Year of Maturity	Dec. 31, 2018
Long-term Debt, Excluding Current Maturities		200.0		200.0
Notes Issued in 1998 with 2018 Maturity Date \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Year of Maturity	Dec. 31, 2018
Long-term Debt, Excluding Current Maturities		200.0		200.0
Notes Issued in 1998 with 2028 Maturity Date \| Senior Notes
Debt Instrument
Year of Maturity	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities		365.8		365.8
Notes Issued in 1998 with 2028 Maturity Date \| Parent Company \| Senior Notes
Debt Instrument
Year of Maturity	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities		365.8		365.8
Notes Issued in 1998 with 2028 Maturity Date \| Minimum \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			6.75%
Notes Issued in 1998 with 2028 Maturity Date \| Minimum \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			6.75%
Notes Issued in 1998 with 2028 Maturity Date \| Maximum \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.25%
Notes Issued in 1998 with 2028 Maturity Date \| Maximum \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.25%
Notes Issued in 2002 \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.375%
Year of Maturity	Dec. 31, 2032
Long-term Debt, Excluding Current Maturities		39.5		39.5
Notes Issued in 2002 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.375%
Year of Maturity	Dec. 31, 2032
Long-term Debt, Excluding Current Maturities		39.5		39.5
Notes Issued in 2009
Debt Instrument
Stated Interest Rate of Debt			7.125%
Year of Maturity	Sep. 30, 2016
Current Maturities of Long-term Debt		0.0		350.0
Notes Issued in 2009 \| Parent Company
Debt Instrument
Stated Interest Rate of Debt			7.125%
Year of Maturity	Dec. 31, 2016
Current Maturities of Long-term Debt		0.0		350.0
Notes Issued in 2010 \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.625%
Year of Maturity	Dec. 31, 2020
Long-term Debt, Excluding Current Maturities		400.0		400.0
Notes Issued in 2010 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.625%
Year of Maturity	Dec. 31, 2020
Long-term Debt, Excluding Current Maturities		400.0		400.0
Notes Issued in 2012 and 2016 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.75%
Year of Maturity	Dec. 31, 2042
Long-term Debt, Excluding Current Maturities		500.0		250.0
Notes Issued in 2012
Debt Instrument
Stated Interest Rate of Debt			5.75%
Long-term Debt, Excluding Current Maturities		250.0
Notes Issued in 2014 \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			4.00%
Year of Maturity	Dec. 31, 2024
Long-term Debt, Excluding Current Maturities		350.0		350.0
Notes Issued in 2014 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			4.00%
Year of Maturity	Dec. 31, 2024
Long-term Debt, Excluding Current Maturities		350.0		350.0
Notes Issued in 2015 \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.875%
Year of Maturity	Dec. 31, 2025
Long-term Debt, Excluding Current Maturities		275.0		275.0
Notes Issued in 2015 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.875%
Year of Maturity	Dec. 31, 2025
Long-term Debt, Excluding Current Maturities		275.0		275.0
Notes Issued in 2016 \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.00%
Year of Maturity	May 15, 2021
Long-term Debt, Excluding Current Maturities		350.0		0.0
Notes Issued in 2016 \| Parent Company \| Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.00%
Year of Maturity	Dec. 31, 2021
Long-term Debt, Excluding Current Maturities		350.0		0.0
Notes Issued 1990 to 1996 \| Medium-term Notes
Debt Instrument
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2023
Debt Instrument, Maturity Date Range, End	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities		50.8		50.8
Notes Issued 1990 to 1996 \| Parent Company \| Medium-term Notes
Debt Instrument
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2023
Debt Instrument, Maturity Date Range, End	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities		50.8		50.8
Notes Issued 1990 to 1996 \| Minimum \| Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Notes Issued 1990 to 1996 \| Minimum \| Parent Company \| Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Notes Issued 1990 to 1996 \| Maximum \| Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.19%
Notes Issued 1990 to 1996 \| Maximum \| Parent Company \| Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.19%
Notes Issued in 1998 with 2038 Maturity Date \| Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt	7.405%		7.405%
Year of Maturity	Dec. 31, 2038
Long-term Debt, Excluding Current Maturities		226.5		226.5
Notes Issued in 1998 with 2038 Maturity Date \| Parent Company \| Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt	7.405%		7.405%
Year of Maturity	Dec. 31, 2038
Long-term Debt, Excluding Current Maturities		$ 226.5		$ 226.5