Subsequent Events	3 Months Ended
Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Event On April 18, 2019 the Corporation terminated its existing revolving credit facility maturing in January 2021 and entered into a new fully undrawn $3.5 billion revolving credit facility with a maturity date of May 15, 2023. This facility can be used for borrowings and letters of credit. Borrowings on the new facility will generally bear interest at 1.30% above the London Interbank Offered Rate (LIBOR), though the interest rate is subject to adjustment if the Corporation’s credit rating changes. The facility is subject to customary representations, warranties and covenants, including a financial covenant limiting the ratio of Total Consolidated Debt to Total Capitalization (as such terms are defined in the credit agreement for the facility) of the Corporation and its consolidated subsidiaries to 0.650 to 1.000, and customary events of default.

The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 855
-URI http://asc.fasb.org/topic&trid=2122774

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