AMN 2017 Annual Report

47 There were no impairment charges recorded during the three years ended December 31, 2017 requiring such measurements. Other Fair Value Measurement Disclosures The Company is required to disclose the fair value of financial instruments that are not recognized at fair value in the consolidated balance sheets for which it is practicable to estimate that value. As of December 31, 2017, the Company’s Notes have a carrying amount of $325,000 and an estimated fair value of $335,156. Quoted market prices in active markets for identical liabilities based inputs (level 1) were used to estimate fair value. The Notes were issued in October 2016 and have a fixed rate of 5.125%. As of December 31, 2016, the Company's Notes approximated their fair value as there had been no changes in available rates for similar debt since the date of issuance. See additional information in Note (8), “Notes Payable and Credit Agreement.” (5) Goodwill and Identifiable Intangible Assets As of December 31, 2017 and 2016, the Company had the following acquired intangible assets: As of December 31, 2017 As of December 31, 2016 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Intangible assets subject to amortization: Staffing databases $ 19,826 $ (7,693) $ 12,133 $ 19,826 $ (5,633) $ 14,193 Customer relationships 136,759 (60,764) 75,995 136,759 (50,309) 86,450 Tradenames and trademarks 61,369 (16,757) 44,612 61,369 (12,139) 49,230 Non-compete agreements 1,697 (958) 739 1,697 (678) 1,019 Acquired technology 8,730 (4,513) 4,217 8,730 (3,298) 5,432 $ 228,381 $ (90,685) $ 137,696 $ 228,381 $ (72,057) $ 156,324 Intangible assets not subject to amortization: Tradenames and trademarks $ 89,400 $ 89,400 $ 227,096 $ 245,724 Aggregate amortization expense for intangible assets was $18,628 and $18,310 for the years ended December 31, 2017 and 2016, respectively. Based on the current amount of intangibles subject to amortization, the estimated future amortization expense as of December 31, 2017 is as follows: Amount Year ending December 31, 2018 $ 17,555 Year ending December 31, 2019 16,827 Year ending December 31, 2020 13,889 Year ending December 31, 2021 11,899 Year ending December 31, 2022 11,640 Thereafter 65,886 $ 137,696