6. Mortgage Notes Payable, Net

The Company had outstanding mortgage notes payable totaling approximately $3.0 billion and $3.0 billion as of December 31, 2018 and 2017, respectively, each collateralized by one or more buildings and related land included in real estate assets. The mortgage notes payable are generally due in monthly installments and mature at various dates through June 9, 2027.

Fixed rate mortgage notes payable totaled approximately $3.0 billion and $3.0 billion at December 31, 2018 and 2017, respectively, with contractual interest rates ranging from 3.43% to 7.69% per annum at December 31, 2018 and December 31, 2017 (with a weighted-average interest rate of 3.77% and 3.78% per annum at December 31, 2018 and 2017, respectively). There were no variable rate mortgage loans at December 31, 2018 and 2017.

No mortgage loans at December 31, 2018 and December 31, 2017 had been accounted for at fair value. Prior to December 31, 2017, the Company had mortgage loans that were accounted for at fair value and the impact of recording them at fair value resulted in a decrease to interest expense of approximately $19.6 million and $46.4 million for the years ended December 31, 2017 and 2016, respectively.

Contractual aggregate principal payments of mortgage notes payable at December 31, 2018 are as follows (in thousands):



	Principal Payments
2019	$	19,670
2020	20,766
2021	40,182
2022	614,710
2023	—
Thereafter	2,300,000
Total aggregate principal payments	2,995,328
Deferred financing costs, net	(30,756		)
Total carrying value of mortgage notes payable, net	$	2,964,572