(6) Debt Commitments

Credit Facility, Notes Payable, and Commitments

Debt obligations and letters of credit outstanding at the end of each period consisted of the following:



	June 30, 2018			December 31, 2017
Outstanding loans under unsecured revolving credit facility	$	290.0		280.0
2.00% Senior unsecured promissory note payable	40.0			40.0
2.45% Senior unsecured promissory note payable	35.0			35.0
3.22% Senior unsecured promissory note payable	60.0			60.0
Total debt	425.0			415.0
Less: Current portion of debt	(2.5		)	(3.0	)
Long-term debt	$	422.5		412.0

Outstanding letters of credit under unsecured revolving credit facility - contingent obligation	$	36.3		36.3

Unsecured Revolving Credit Facility

We have a $700.0 committed unsecured revolving credit facility ('Credit Facility'). The Credit Facility includes a committed letter of credit subfacility of $55.0. The commitments under the Credit Facility will expire (and any borrowings outstanding under the Credit Facility will become due and payable) on March 10, 2020. In the next twelve months, we have the ability and intent to repay a portion of the outstanding loans using cash; therefore, we have classified this portion as a current liability. The Credit Facility contains certain financial and other covenants, and our right to borrow under the Credit Facility is conditioned upon, among other things, our compliance with these covenants. We are currently in compliance with these covenants.

Borrowings under the Credit Facility generally bear interest at a rate per annum equal to the London Interbank Offered Rate ('LIBOR') for interest periods of various lengths selected by us, plus 0.95%. Based on the interest periods we have chosen, our weighted per annum interest rate at June 30, 2018 was approximately 3.0%. We pay a commitment fee for the unused portion of the Credit Facility. This fee is either 0.10% or 0.125% per annum based on our usage of the Credit Facility.

Senior Unsecured Promissory Notes Payable

On July 20, 2016 (the 'Effective Date'), we entered into a master note agreement (the 'Master Note Agreement') with certain institutional lenders, pursuant to which, during the period commencing on the Effective Date and ending three years thereafter, we may issue at our discretion in private placements, and the institutional lenders may purchase at their discretion, senior unsecured promissory notes of the company (the 'Notes') in the aggregate principal amount outstanding from time to time of up to $200.0. The Notes will bear interest at either a fixed rate, or a floating rate based on LIBOR for an interest period of one, three, or six months. The Notes will mature no later than 12 years after the date of issuance thereof, in the case of fixed rate Notes, or 10 years after the date of issuance thereof, in the case of floating rate Notes. All of the Notes will be prepayable at our option in whole or in part. The Master Note Agreement contains certain financial and other covenants. We are currently in compliance with these covenants.

Three series of Notes are currently outstanding under the Master Note Agreement. The first series of Notes ('Series A'), was issued on the Effective Date, is in an aggregate principal amount of $40.0, is due and payable in full on July 20, 2021, and bears interest at a fixed rate of 2.00% per annum. The second series of Notes ('Series B'), was issued on the Effective Date, is in an aggregate principal amount of $35.0, is due and payable in full on July 20, 2022, and bears interest at a fixed rate of 2.45% per annum. The third series of Notes ('Series C'), was issued on March 1, 2017, is in an aggregate principal amount of $60.0, is due and payable in full on March 1, 2024, and bears interest at a fixed rate of 3.22% per annum. There is no amortization of these Notes prior to their maturity dates. Interest on the Notes is payable quarterly in arrears on January 20, April 20, July 20, and October 20 of each year. The carrying value of the Notes approximates fair value. The fair value was based on available external pricing data and current market rates for similar debt instruments, among other factors, which are classified as a Level 2 measurement under the fair value hierarchy.