Debt

6 Months Ended

Jun. 30, 2019

Debt Disclosure [Abstract]

Debt

13. Debt

For the six months ended June 30, 2019 and 2018, cash payments for interest were $45.8 million and $51.1 million, respectively.

Included in interest expense, net are amortization of treasury lock settlements and amortization of financing costs. For both the three months ended June 30, 2019 and 2018, amortization of treasury lock settlements was $1.3 million, and for the six months ended June 30, 2019 and 2018, amortization of treasury locks was $2.6 million and $2.7 million, respectively. For both the three months ended June 30, 2019 and 2018, amortization of financing costs was $0.7 million, and during the six months ended June 30, 2019 and 2018, amortization of financing costs was $1.4 million and $1.3 million, respectively.

At June 30, 2019, we had $2,496.7 million of fixed-rate senior notes outstanding. The fair value of our fixed-rate debt was estimated to be $2,582.2 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 2018 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 2018 Annual Report on Form 10-K.