The following table presents the Company’s total revenues separated between revenues from contracts with customers and other sources of revenues (in thousands):

	Three Months Ended March 31, 2019		Three Months Ended March 31, 2018
Revenue from contracts with customers:
Commissions	$	429,520	$	407,857
Data, software, and post-trade		17,910		15,099
Fees from related parties		5,795		6,299
Other revenues		2,775		—
Total revenue from contracts with customers		456,000		429,255
Other sources of revenue:
Principal transactions		84,230		91,918
Interest income		3,665		2,675
Other revenues		856		926
Total revenues	$	544,751	$	524,774

As discussed in Note 1 – “Organization and Basis of Presentation”, the Company adopted the new revenue recognition standard, as codified within ASC Topic 606, as of January 1, 2018. There was no significant impact to the Company’s unaudited condensed consolidated financial statements for the three months ended March 31, 2018 as a result of applying the new revenue recognition standard.

Refer to Note 3—“Summary of Significant Accounting Policies,” in our consolidated financial statements included in Part II, Item 8 of our Annual Report on Form 10-K for the year ended December 31, 2018 for detailed information on the recognition of the Company’s revenues from contracts with customers.

Refer to Note 22 – “Segment, Geographic and Product Information,” for a further discussion on the allocation of revenues to geographic regions.

The timing of our revenue recognition may differ from the timing of payment by our customers. The Company records a receivable when revenue is recognized prior to payment and the Company has an unconditional right to payment. Alternatively, when payment precedes the provision of the related services, the Company records deferred revenue until the performance obligations are satisfied.

The Company had receivables related to revenues from contracts with customers of $604.2 million and $516.1 million at March 31, 2019 and December 31, 2018, respectively. The Company had no impairments related to these receivables during the three months ended March 31, 2019 and 2018.

The Company’s deferred revenue primarily relates to customers paying advance or billed in advance where the performance obligation has not yet been satisfied. Deferred revenue at March 31, 2019 and December 31, 2018 was $15.2 million and $12.8 million, respectively. During the three months ended March 31, 2019 and 2018, the Company recognized revenue of $6.3 million and $7.5 million, respectively, that was recorded as deferred revenue at the beginning of the period.

The Company capitalizes costs to fulfill contracts associated with different lines of its business where the revenue is recognized at a point in time and the costs are determined to be recoverable. Capitalized costs to fulfill a contract are recognized at the point in time that the related revenue is recognized.

At March 31, 2018, there were $2.2 million of capitalized costs recorded to fulfill a contract. At December 31, 2018, there were no capitalized costs recorded to fulfill a contract.