Debt

3 Months Ended

Mar. 31, 2021

Debt Disclosure [Abstract]

Debt

11. Debt

For the three months ended March 31, 2021 and 2020, cash payments for interest were $7.5 million and $7.3 million, respectively.

Included in interest expense, net is the amortization of financing costs. For both the three months ended March 31, 2021 and 2020, amortization of financing costs was $0.5 million.

At March 31, 2021, we had $2,493.8 million of fixed-rate senior notes outstanding. The fair value of our fixed-rate debt was estimated to be $2,719.0 million. The difference between the book value and fair value is due to the difference between the period-end market interest rate and the stated rate of our fixed-rate debt. We estimated the fair value of our fixed-rate debt using quoted market prices (Level 2 inputs) within the fair value hierarchy, which is further defined in Note 2, Summary of Significant Accounting Policies, of the Notes to Consolidated Financial Statements in "Part II, Item 8. Financial Statements and Supplementary Data" of our 2020 Annual Report on Form 10-K.

For more information on our long-term debt and interest rates on that debt, see Note 10, Debt, of the Notes to Consolidated Financial Statements in "Part II, Item 8. Financial Statements and Supplementary Data" of our 2020 Annual Report on Form 10-K.