Debt	9 Months Ended
Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	DEBT Debt Issuance. On March 7, 2018, the Company issued $500 million aggregate principal amount of 4.05% senior notes that will mature on March 7, 2048. The net proceeds of the issuance, after the deduction of the underwriting discount and expenses payable by the Company, totaled approximately $491 million. Interest on the senior notes is payable semi-annually in arrears on March 7 and September 7. Prior to September 7, 2047, the senior notes may be redeemed, in whole or in part, at the Company’s option, at any time or from time to time, at a redemption price equal to the greater of (a) 100% of the principal amount of any senior notes to be redeemed or (b) the sum of the present values of the remaining scheduled payments of principal and interest to but excluding September 7, 2047 on any senior notes to be redeemed (exclusive of interest accrued to the date of redemption) discounted to the date of redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the then current Treasury rate (as defined in the senior notes), plus 15 basis points. On or after September 7, 2047, the senior notes may be redeemed, in whole or in part, at the Company’s option, at any time or from time to time, at a redemption price equal to100% of the principal amount of any senior notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. Debt Repayment. On May 15, 2018, the Company's $500 million, 5.80% senior notes matured and were fully paid. Credit Agreement. On June 4, 2018, the Company entered into a five-year, $1.0 billion revolving credit agreement with a syndicate of financial institutions, replacing its five-year $1.0 billion credit agreement that was due to expire on June 7, 2018. Pursuant to the credit agreement covenants, the Company must maintain a minimum consolidated net worth, defined as shareholders’ equity determined in accordance with GAAP (excluding accumulated other comprehensive income (loss)) plus (a) trust preferred securities (not to exceed 15% of total capital) and (b) mandatorily convertible securities (combined with trust preferred securities, not to exceed 25% of total capital), less goodwill and other intangible assets. That threshold is adjusted downward by an amount equal to 70% of the aggregate amount of common stock repurchased by the Company after March 31, 2018, up to a maximum deduction of $1.75 billion. The threshold was $13.719 billion at September 30, 2018 and could decline to a minimum of $12.494 billion during the term of the credit agreement, subject to the Company repurchasing an additional $1.75 billion of its common stock. In addition, the credit agreement contains other customary restrictive covenants as well as certain customary events of default, including with respect to a change in control, which would occur upon the acquisition of 35% or more of the Company’s voting stock or certain changes in the composition of the Company’s Board of Directors. At September 30, 2018, the Company was in compliance with these covenants. Generally, the cost of borrowing under this agreement will range from LIBOR plus 75 basis points to LIBOR plus 137.5 basis points, depending on the Company’s credit ratings. At September 30, 2018, that cost would have been LIBOR plus 100 basis points, had there been any amounts outstanding under the credit agreement. Commercial Paper. The Company had $100 million of commercial paper outstanding at both September 30, 2018 and December 31, 2017.

DEBT

Debt Issuance. On March 7, 2018, the Company issued $500 million aggregate principal amount of 4.05% senior notes that will mature on March 7, 2048. The net proceeds of the issuance, after the deduction of the underwriting discount and expenses payable by the Company, totaled approximately $491 million. Interest on the senior notes is payable semi-annually in arrears on March 7 and September 7. Prior to September 7, 2047, the senior notes may be redeemed, in whole or in part, at the Company’s option, at any time or from time to time, at a redemption price equal to the greater of (a) 100% of the principal amount of any senior notes to be redeemed or (b) the sum of the present values of the remaining scheduled payments of principal and interest to but excluding September 7, 2047 on any senior notes to be redeemed (exclusive of interest accrued to the date of redemption) discounted to the date of redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the then current Treasury rate (as defined in the senior notes), plus 15 basis points. On or after September 7, 2047, the senior notes may be redeemed, in whole or in part, at the Company’s option, at any time or from time to time, at a redemption price equal to100% of the principal amount of any senior notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.

Debt Repayment. On May 15, 2018, the Company's $500 million, 5.80% senior notes matured and were fully paid.

Credit Agreement. On June 4, 2018, the Company entered into a five-year, $1.0 billion revolving credit agreement with a syndicate of financial institutions, replacing its five-year $1.0 billion credit agreement that was due to expire on June 7, 2018. Pursuant to the credit agreement covenants, the Company must maintain a minimum consolidated net worth, defined as shareholders’ equity determined in accordance with GAAP (excluding accumulated other comprehensive income (loss)) plus (a) trust preferred securities (not to exceed 15% of total capital) and (b) mandatorily convertible securities (combined with trust preferred securities, not to exceed 25% of total capital), less goodwill and other intangible assets. That threshold is adjusted downward by an amount equal to 70% of the aggregate amount of common stock repurchased by the Company after March 31, 2018, up to a maximum deduction of $1.75 billion. The threshold was $13.719 billion at September 30, 2018 and could decline to a minimum of $12.494 billion during the term of the credit agreement, subject to the Company repurchasing an additional $1.75 billion of its common stock. In addition, the credit agreement contains other customary restrictive covenants as well as certain customary events of default, including with respect to a change in control, which would occur upon the acquisition of 35% or more of the Company’s voting stock or certain changes in the composition of the Company’s Board of Directors. At September 30, 2018, the Company was in compliance with these covenants. Generally, the cost of borrowing under this agreement will range from LIBOR plus 75 basis points to LIBOR plus 137.5 basis points, depending on the Company’s credit ratings. At September 30, 2018, that cost would have been LIBOR plus 100 basis points, had there been any amounts outstanding under the credit agreement.

Commercial Paper. The Company had $100 million of commercial paper outstanding at both September 30, 2018 and December 31, 2017.