Fair Value Measurements
 9 Months Ended
Sep. 30, 2016
Fair Value Disclosures [Abstract]  
Fair Value Measurements
Fair Value Measurements
Financial assets and liabilities are recorded at fair value. The carrying amounts of certain of the Company's financial instruments, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable, and accrued liabilities and deferred revenue, approximate their fair value due to their short maturities. Short-term and long-term debt are reported at their respective amortized cost on its condensed consolidated balance sheets. The remaining financial instruments are reported on its condensed consolidated balance sheets at amounts that approximate current fair values. 
The following tables present information about the Company’s financial assets measured at fair value on a recurring basis as of September 30, 2016, and December 31, 2015, and indicate the fair value hierarchy of the valuation techniques utilized by the Company to determine such fair value. As a basis for categorizing inputs, the Company uses a three-tier fair value hierarchy, which prioritizes the inputs used to measure fair value from market-based assumptions to entity specific assumptions:
Level 1: Inputs which include quoted prices in active markets for identical assets or liabilities;
Level 2: Inputs, other than level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and
Level 3: Unobservable inputs that are supported by little or no market activity, which require the reporting entity to develop its own assumptions.
None of the Company’s non-financial assets and liabilities are recorded at fair value on a non-recurring basis. No transfers between fair value hierarchy levels have occurred during the periods presented.
Assets measured at fair value on a recurring basis as of September 30, 2016 consisted of the following (in thousands):
 
Balance as of
September 30,
2016
 
Quoted Prices
in Active
Markets for
Identical Assets
(Level 1)
 
Significant
Other
Observable
Inputs
(Level 2)
 
Significant
Unobservable
Inputs
(Level 3)
Assets:
 
 
 
 
 
 
 
Money market funds
$
28,599

 
$
28,599

 
$
—

 
$
—

Commercial paper
1,493

 
—

 
1,493

 
—

Corporate debt securities
3,008

 
—

 
3,008

 
—

 
$
33,100

 
$
28,599

 
$
4,501

 
$
—

Assets measured at fair value on a recurring basis as of December 31, 2015 consisted of the following (in thousands):
 
Balance as of
December 31,
2015
 
Quoted Prices
in Active
Markets for
Identical Assets
(Level 1)
 
Significant
Other
Observable
Inputs
(Level 2)
 
Significant
Unobservable
Inputs
(Level 3)
Assets:
 
 
 
 
 
 
 
Money market funds
$
34,806

 
$
34,806

 
$
—

 
$
—

Corporate debt securities
7,415

 
—

 
7,415

 
—

 
$
42,221

 
$
34,806

 
$
7,415

 
$
—


The Company estimates the fair value of commercial paper and corporate debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker quotes on the same or similar securities; issuer credit spreads; benchmark securities; prepayment or default projections based on historical data; and other observable inputs.

The estimated fair value of the Company's notes payable, considering level 2 inputs, approximates their carrying value based upon the borrowing terms and conditions currently available to the Company.