First Trust NASDAQ-100-Technology Sector Index Fund Average Annual Total Returns		12 Months Ended	28 Months Ended	34 Months Ended	38 Months Ended	58 Months Ended	59 Months Ended	60 Months Ended	89 Months Ended	101 Months Ended	120 Months Ended	132 Months Ended	227 Months Ended	229 Months Ended	234 Months Ended		236 Months Ended	237 Months Ended	238 Months Ended	268 Months Ended
	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025
Nasdaq-100 Technology Sector(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent		23.14%						11.47%			19.67%						14.46%
S&P 500® Index (reflects no deduction for fees, expenses or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent		17.88%	21.88%	24.47%	21.49%	14.19%	14.00%	14.42%	14.37%	14.77%	14.82%	10.87%	11.26%	10.73%	11.26%	11.13%	10.87%	10.96%	10.98%	11.07%
S&P 500® Information Technology Index (reflects no deduction for fees, expenses or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent		24.04%						20.91%			24.30%						16.58%
First Trust NASDAQ-100-Technology Sector Index Fund
Prospectus [Line Items]
Average Annual Return, Percent		22.44%						10.83%			18.95%						13.75%
Performance Inception Date	Apr. 19, 2006
First Trust NASDAQ-100-Technology Sector Index Fund \| After Taxes on Distributions
Prospectus [Line Items]
Average Annual Return, Percent		22.44%						10.80%			18.70%						13.53%
First Trust NASDAQ-100-Technology Sector Index Fund \| After Taxes on Distributions and Sales
Prospectus [Line Items]
Average Annual Return, Percent		13.29%						8.61%			16.18%						12.14%