| Summary of Significant Classes of Amortizable Intangible Assets |
The following tables provide details, by major category, of the significant classes of amortizable intangible assets: | | | As of March 31, 2016 | | | | | | | | Accumulated | | | | | | | | Cost | | Amortization | | Net | | | | | (Dollars in thousands) | | | Customer lists and contracts | | $ | 22,403 | | $ | (19,220) | | $ | 3,183 | | | Domain and brand names | | | 17,358 | | | (11,593) | | | 5,765 | | | Favorable and assigned leases | | | 2,379 | | | (1,909) | | | 470 | | | Subscriber base and lists | | | 7,313 | | | (4,162) | | | 3,151 | | | Author relationships | | | 2,245 | | | (1,559) | | | 686 | | | Non-compete agreements | | | 1,323 | | | (818) | | | 505 | | | Other amortizable intangible assets | | | 1,336 | | | (1,336) | | | | | | | | $ | 54,357 | | $ | (40,597) | | $ | 13,760 | | | | | As of December 31, 2015 | | | | | | | | Accumulated | | | | | | | | Cost | | Amortization | | Net | | | | | (Dollars in thousands) | | | Customer lists and contracts | | $ | 20,009 | | $ | (18,914) | | $ | 1,095 | | | Domain and brand names | | | 16,619 | | | (11,200) | | | 5,419 | | | Favorable and assigned leases | | | 2,379 | | | (1,887) | | | 492 | | | Subscriber base and lists | | | 7,313 | | | (3,808) | | | 3,505 | | | Author relationships | | | 2,245 | | | (1,523) | | | 722 | | | Non-compete agreements | | | 1,034 | | | (786) | | | 248 | | | Other amortizable intangible assets | | | 1,336 | | | (1,336) | | | | | | | | $ | 50,935 | | $ | (39,454) | | $ | 11,481 | |
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| Amortizable Intangible Assets, Estimate Amortization Expense |
Based on the amortizable intangible assets as of March 31, 2016, we estimate amortization expense for the next five years to be as follows: | Year Ending December 31, | | Amortization Expense | | | | | (Dollars in thousands) | | | 2016 (April Dec) | | $ | 3,405 | | | 2017 | | | 3,285 | | | 2018 | | | 3,042 | | | 2019 | | | 2,529 | | | 2020 | | | 1,229 | | | Thereafter | | | 270 | | | Total | | $ | 13,760 | |
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