The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at September 30, 2018 and December 31, 2017 (in thousands):

	September 30, 2018			December 31, 2017			Effective Interest Rate		Maturity Date
MORTGAGE DEBT:
Two Logan Square	$	83,220		$	84,440		3.98%		May 2020
Four Tower Bridge		9,583			-		4.50%	(a)	Feb 2021
One Commerce Square		121,066			123,667		3.64%		Apr 2023
Two Commerce Square		111,017			112,000		4.51%		Apr 2023
Principal balance outstanding		324,886			320,107
Plus: fair market value premium (discount), net		(1,853	)		(2,325	)
Less: deferred financing costs		(445	)		(566	)
Mortgage indebtedness	$	322,588		$	317,216

UNSECURED DEBT
Seven-Year Term Loan - Swapped to fixed	$	250,000		$	250,000		3.72%		Oct 2022
$350.0M 3.95% Guaranteed Notes due 2023		350,000			350,000		3.87%		Feb 2023
$250.0M 4.10% Guaranteed Notes due 2024		250,000			250,000		4.33%		Oct 2024
$450.0M 3.95% Guaranteed Notes due 2027		450,000			450,000		4.03%		Nov 2027
$250.0M 4.55% Guaranteed Notes due 2029		250,000			250,000		4.60%		Oct 2029
Indenture IA (Preferred Trust I)		27,062			27,062		LIBOR + 1.25%		Mar 2035
Indenture IB (Preferred Trust I) - Swapped to fixed		25,774			25,774		3.30%		Apr 2035
Indenture II (Preferred Trust II) - Swapped to fixed		25,774			25,774		3.09%		Jul 2035
Principal balance outstanding		1,628,610			1,628,610
Plus: original issue premium (discount), net		(4,178	)		(4,423	)
Less: deferred financing costs		(9,483	)		(10,575	)
Total unsecured indebtedness	$	1,614,949		$	1,613,612
Total Debt Obligations	$	1,937,537		$	1,930,828

As of September 30, 2018 and December 31, 2017, the Company’s weighted-average effective interest rates on its mortgage notes payable were 4.05% and 4.04%, respectively.

On July 17, 2018, the Company executed the Amended and Restated Revolving Credit Agreement (as amended and restated, the “2018 Credit Facility”). The amendment and restatement, among other things: (i) maintained the total commitment of the revolving line of credit of $600.0 million; (ii) extended the maturity date from May 15, 2019 to July 15, 2022, with two six-month extensions at the Company’s election subject to specified conditions and subject to payment of an extension fee; (iii) reduced the interest rate margins applicable to Eurodollar loans; (iv) provided for an additional interest rate option based on a floating LIBOR rate; and (v) removed the covenant requiring the Company to maintain a minimum net worth. In connection with the amendments, the Company capitalized $2.7 million in financing costs, which will be amortized through the July 15, 2022 maturity date.

At the Company's option, loans outstanding under the 2018 Credit Facility will bear interest at a rate per annum equal to (1) LIBOR plus between 0.775% and 1.45%, based on the Company's credit rating, or (2) a base rate equal to the greatest of (a) the Administrative Agent's prime rate, (b) the Federal Funds rate plus 0.5% or (c) LIBOR for a one month period plus 1.00%, in each case, plus a margin ranging from 0.0% to 0.45% based on the Company's credit rating. The 2018 Credit Facility also contains a competitive bid option that allows banks that are part of the lender consortium to bid to make loan advances to the Company at a reduced interest rate. In addition, the Company is also obligated to pay (1) in quarterly installments a facility fee on the total commitment at a rate per annum ranging from 0.125% to 0.30% based on the Company's credit rating and (2) an annual fee on the undrawn amount of each letter or credit equal to the LIBOR Margin. Based on the Company's current credit rating, the LIBOR margin is 1.10% and the facility fee is 0.25%.

The terms of the 2018 Credit Facility require that the Company maintain customary financial and other covenants, including: (i) a fixed charge coverage ratio greater than or equal to 1.5 to 1.00; (ii) a leverage ratio less than or equal to 0.60 to 1.00, subject to specified exceptions; (iii) a ratio of unsecured indebtedness to unencumbered asset value less than or equal to 0.60 to 1.00, subject to specified exceptions; (iv) a ratio of secured indebtedness to total asset value less than or equal to 0.40 to 1.00; and (v) a ratio of unencumbered cash flow to interest expense on unsecured debt greater than 1.75 to 1.00. In addition, the Credit Facility restricts payments of dividends and distributions on shares in excess of 95% of the Company's funds from operations (FFO) except to the extent necessary to enable the Company to continue to qualify as a REIT for Federal income tax purposes.

The Company had no borrowings under the 2018 Credit Facility as of and during the nine-month period ended September 30, 2018. As of September 30, 2017, the Company had $178.0 million of borrowings under the Credit Facility and $13.5 million in letters of credit outstanding. During the nine months ended September 30, 2017, the weighted-average interest rate on Credit Facility borrowings was 2.34%. As of September 30, 2017, the effective interest rate on Credit Facility borrowings was 2.43%.

Concurrently with its entry into the 2018 Credit Facility, the Company terminated its then existing unsecured revolving credit facility, which had a scheduled maturity date of May 15, 2019. The Parent Company unconditionally guarantees the unsecured debt obligations of the Operating Partnership (or is a co-borrower with the Operating Partnership) but does not by itself incur unsecured indebtedness. The Parent Company has no material assets other than its investment in the Operating Partnership.

The Company was in compliance with all financial covenants as of September 30, 2018. Management continuously monitors the Company’s current and anticipated compliance with the covenants. Certain of the covenants restrict the Company’s ability to obtain alternative sources of capital.

As of September 30, 2018, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands):