Fair Value Measurements	6 Months Ended
Fair Value Measurements	Jun. 30, 2018
Fair Value Measurements
Fair Value Measurements	Note 7.Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring and Non-recurring Basis The Company had no assets or liabilities which are measured at fair value on a recurring or non-recurring basis as of June 30, 2018 or December 31, 2017. Financial Instruments Not Measured at Fair Value The fair value of debt financing is estimated based on the quoted market prices for the same or similar issues, or on the current rates offered to the Company for debt of the same remaining maturities, which would be categorized as a Level 2 measurement in the fair value hierarchy. The estimated fair value of debt financing as of June 30, 2018 was approximately $10.9 billion compared to a book value of $11.1 billion. The estimated fair value of debt financing as of December 31, 2017 was $10.0 billion compared to a book value of $9.8 billion. The following financial instruments are not measured at fair value on the Company’s consolidated balance sheet at June 30, 2018, but require disclosure of their fair values: cash and cash equivalents and restricted cash. The estimated fair value of such instruments at June 30, 2018 and December 31, 2017 approximates their carrying value as reported on the consolidated balance sheet. The fair value of all these instruments would be categorized as Level 1 in the fair value hierarchy.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.