Debt Instrument, Covenant Default, Amount of Non-Payment

No definition available.

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- Definition

Undrawn outstanding letters of credit between subsidiaries of the Company.

+ References

No definition available.

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- Definition

Undrawn outstanding letters of credit in favor of third parties.

+ References

No definition available.

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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

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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- Definition

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

+ References

+ Details

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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.

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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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

+ Details

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- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

+ Details

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- Definition

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.

+ References

+ Details

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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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-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
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
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-Name Accounting Standards Codification
-Topic 470
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-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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- Definition

The cash inflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes proceeds from (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

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Debt (Narrative) (Details) - USD ($)	12 Months Ended
Debt (Narrative) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2006
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 22,218,000	$ 15,081,000
Undrawn Outstanding Letters Of Credit In Favor Of Third Parties	189,400,000	132,200,000
Undrawn Outstanding Letters Of Credit Between Subsidiaries	1,010,800,000	$ 1,127,400,000
Debt Instrument, Face Amount				$ 850,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity	$ 741,600,000.0
Debt, Weighted Average Interest Rate	5.16%	5.20%
Debt Instrument, Covenant Default, Amount of Non-Payment	$ 100,000,000
Long-term Debt, Gross	3,110,853,000	$ 2,312,629,000
Long-term debt	3,088,635,000	2,297,548,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	2,919,000
Line of Credit Facility, Commitment Fee Amount	7,900,000	10,900,000	$ 12,600,000
Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 8,800,000
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Debt Instrument, Maturity Date	Dec. 31, 2026
Debt Instrument, Face Amount	$ 400,000,000
Proceeds from Issuance of Long-term Debt and Capital Securities, Net	791,200,000
Long-term Debt, Gross	$ 399,985,000	0
Subordinated Debentures Due 2056 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Debt Instrument, Maturity Date	Dec. 31, 2056
Debt Instrument, Face Amount	$ 400,000,000.0
Long-term Debt, Gross	$ 400,000,000	0
Junior Subordinated Debentures Due 2065 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2065
Debt Instrument, Face Amount	$ 400,000,000
Long-term Debt, Gross	$ 318,737,000	318,734,000
Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Debt Instrument, Maturity Date	Dec. 31, 2021
Debt Instrument, Face Amount	$ 400,000,000
Long-term Debt, Gross	$ 399,025,000	398,803,000
Subordinated Debentures Due 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.20%
Debt Instrument, Maturity Date	Dec. 31, 2042
Debt Instrument, Face Amount	$ 400,000,000
Long-term Debt, Gross	$ 400,000,000	400,000,000
Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Debt Instrument, Maturity Date	Dec. 31, 2023
Debt Instrument, Face Amount	$ 400,000,000
Long-term Debt, Gross	$ 398,986,000	398,835,000
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.09%
Debt Instrument, Maturity Date	Dec. 31, 2039
Debt Instrument, Face Amount	$ 100,000,000
Long-term Debt, Gross	$ 94,370,000	96,849,000
Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Debt Instrument, Maturity Date	Dec. 31, 2019
Debt Instrument, Face Amount	$ 400,000,000
Long-term Debt, Gross	$ 399,805,000	399,737,000
Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.625%
Debt Instrument, Maturity Date	Dec. 31, 2017
Debt Instrument, Face Amount	$ 300,000,000.0
Long-term Debt, Gross	299,945,000	299,671,000
Syndicated Credit Facility $850 Million [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	850,000,000
Long-term Line of Credit	$ 96,095,000	$ 313,659,000