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 September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Revenue from contracts with customers:
Commissions	$	409,082	$	351,969	$	1,259,571	$	1,138,313
Data, software, and post-trade		18,364		16,547		55,015		47,016
Fees from related parties		8,208		6,821		21,224		19,054
Other revenues		3,637		30		8,728		30
Total revenue from contracts with customers		439,291		375,367		1,344,538		1,204,413
Other sources of revenue:
Principal transactions		75,536		73,360		250,198		250,266
Interest income		3,976		2,870		15,454		10,485
Other revenues		2,334		4,045		6,885		6,295
Total revenues	$	521,137	$	455,642	$	1,617,075	$	1,471,459

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 periods presented 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 $543.6 million and $516.1 million at September 30, 2019 and December 31, 2018, respectively. The Company had no impairments related to these receivables during the three and nine months ended September 30, 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 September 30, 2019 and December 31, 2018 was $15.6 million and $12.8 million, respectively. During the three months ended September 30, 2019 and 2018, the Company recognized revenue of $7.3 million and $5.1 million, respectively, that was recorded as deferred revenue at the beginning of the period. During the nine months ended September 30, 2019 and 2018, the Company recognized revenue of $8.8 million and $5.6 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 September 30, 2019, there were $1.7 million of capitalized costs recorded to fulfill a contract. At December 31, 2018, there were no capitalized costs recorded to fulfill a contract.