| Shareholder Report | 12 Months Ended | 88 Months Ended | 109 Months Ended |
| Jul. 31, 2024 USD ($) Holding | Jul. 31, 2024 USD ($) Holding | Jul. 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | | | |
| Document Type | N-CSR | | |
| Amendment Flag | false | | |
| Registrant Name | LORD ABBETT DEVELOPING GROWTH FUND, INC. | | |
| Entity Central Index Key | 0000276914 | | |
| Entity Investment Company Type | N-1A | | |
| Document Period End Date | Jul. 31, 2024 | | |
| C000018473 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class A | | |
| Trading Symbol | LAGWX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B19"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class A $98 0.94% | | |
| Expenses Paid, Amount | $ 98 | | |
| Expense Ratio, Percent | 0.94% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.91%, reflecting performance at the net asset value (NAV) of Class A shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B24"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class A with load Russell 2000 Growth Index S&P 500 Index 7/31/2014 $9,424 $10,000 $10,000 8/31/2014 $9,934 $10,558 $10,400 9/30/2014 $9,563 $9,992 $10,254 10/31/2014 $10,128 $10,612 $10,505 11/30/2014 $10,224 $10,681 $10,787 12/31/2014 $10,289 $10,997 $10,760 1/31/2015 $10,020 $10,746 $10,437 2/28/2015 $10,817 $11,520 $11,037 3/31/2015 $11,021 $11,727 $10,862 4/30/2015 $10,646 $11,382 $10,966 5/31/2015 $11,202 $11,800 $11,108 6/30/2015 $11,309 $11,958 $10,892 7/31/2015 $11,332 $12,007 $11,121 8/31/2015 $10,141 $11,097 $10,450 9/30/2015 $9,534 $10,396 $10,191 10/31/2015 $9,617 $10,986 $11,051 11/30/2015 $9,846 $11,389 $11,084 12/31/2015 $9,374 $10,846 $10,909 1/31/2016 $8,165 $9,670 $10,368 2/29/2016 $7,946 $9,602 $10,354 3/31/2016 $8,409 $10,338 $11,056 4/30/2016 $8,353 $10,441 $11,099 5/31/2016 $8,586 $10,722 $11,298 6/30/2016 $8,597 $10,673 $11,327 7/31/2016 $9,277 $11,371 $11,745 8/31/2016 $9,369 $11,491 $11,762 9/30/2016 $9,531 $11,657 $11,764 10/31/2016 $8,856 $10,932 $11,549 11/30/2016 $9,303 $11,911 $11,977 12/31/2016 $9,120 $12,073 $12,214 1/31/2017 $9,491 $12,269 $12,445 2/28/2017 $9,841 $12,570 $12,939 3/31/2017 $9,882 $12,719 $12,954 4/30/2017 $9,958 $12,953 $13,088 5/31/2017 $10,014 $12,835 $13,272 6/30/2017 $10,283 $13,277 $13,355 7/31/2017 $10,471 $13,390 $13,629 8/31/2017 $10,507 $13,374 $13,671 9/30/2017 $11,010 $14,103 $13,953 10/31/2017 $11,345 $14,321 $14,278 11/30/2017 $11,630 $14,732 $14,716 12/31/2017 $11,848 $14,749 $14,880 1/31/2018 $12,305 $15,324 $15,732 2/28/2018 $12,422 $14,888 $15,152 3/31/2018 $12,697 $15,088 $14,767 4/30/2018 $12,976 $15,103 $14,824 5/31/2018 $14,312 $16,054 $15,181 6/30/2018 $14,597 $16,180 $15,274 7/31/2018 $14,526 $16,458 $15,843 8/31/2018 $16,416 $17,482 $16,359 9/30/2018 $16,375 $17,073 $16,452 10/31/2018 $14,079 $14,913 $15,327 11/30/2018 $13,924 $15,146 $15,640 12/31/2018 $12,452 $13,376 $14,228 1/31/2019 $14,416 $14,921 $15,368 2/28/2019 $15,983 $15,885 $15,861 3/31/2019 $15,814 $15,670 $16,169 4/30/2019 $16,199 $16,147 $16,824 5/31/2019 $15,774 $14,949 $15,755 6/30/2019 $17,252 $16,100 $16,865 7/31/2019 $17,759 $16,258 $17,108 8/31/2019 $16,820 $15,556 $16,837 9/30/2019 $15,294 $15,428 $17,152 10/31/2019 $15,625 $15,867 $17,523 11/30/2019 $16,190 $16,801 $18,159 12/31/2019 $16,425 $17,186 $18,707 1/31/2020 $16,785 $16,997 $18,700 2/29/2020 $16,132 $15,770 $17,161 3/31/2020 $13,647 $12,758 $15,041 4/30/2020 $15,906 $14,659 $16,969 5/31/2020 $18,040 $16,044 $17,778 6/30/2020 $19,186 $16,660 $18,131 7/31/2020 $20,466 $17,233 $19,153 8/31/2020 $21,646 $18,244 $20,530 9/30/2020 $22,240 $17,853 $19,750 10/31/2020 $22,775 $17,989 $19,225 11/30/2020 $25,748 $21,161 $21,329 12/31/2020 $28,345 $23,138 $22,149 1/31/2021 $29,550 $24,254 $21,926 2/28/2021 $30,663 $25,055 $22,530 3/31/2021 $28,808 $24,267 $23,517 4/30/2021 $30,107 $24,796 $24,772 5/31/2021 $28,270 $24,087 $24,945 6/30/2021 $29,634 $25,217 $25,527 7/31/2021 $29,077 $24,299 $26,134 8/31/2021 $29,847 $24,740 $26,929 9/30/2021 $28,549 $23,792 $25,676 10/31/2021 $30,153 $24,906 $27,475 11/30/2021 $27,686 $23,689 $27,285 12/31/2021 $27,592 $23,794 $28,507 1/31/2022 $22,421 $20,605 $27,032 2/28/2022 $22,432 $20,695 $26,223 3/31/2022 $22,275 $20,790 $27,196 4/30/2022 $19,289 $18,239 $24,825 5/31/2022 $18,748 $17,895 $24,870 6/30/2022 $17,562 $16,787 $22,818 7/31/2022 $19,248 $18,666 $24,921 8/31/2022 $19,196 $18,491 $23,905 9/30/2022 $17,666 $16,827 $21,703 10/31/2022 $18,759 $18,425 $23,461 11/30/2022 $18,811 $18,725 $24,772 12/31/2022 $17,635 $17,523 $23,344 1/31/2023 $19,113 $19,266 $24,811 2/28/2023 $18,936 $19,057 $24,206 3/31/2023 $19,102 $18,587 $25,095 4/30/2023 $18,634 $18,371 $25,486 5/31/2023 $18,936 $18,374 $25,597 6/30/2023 $19,726 $19,898 $27,288 7/31/2023 $19,976 $20,828 $28,165 8/31/2023 $18,603 $19,744 $27,717 9/30/2023 $17,167 $18,442 $26,395 10/31/2023 $15,700 $17,019 $25,840 11/30/2023 $17,344 $18,569 $28,200 12/31/2023 $19,133 $20,792 $29,481 1/31/2024 $19,227 $20,125 $29,977 2/29/2024 $21,017 $21,760 $31,577 3/31/2024 $21,547 $22,369 $32,593 4/30/2024 $20,236 $20,646 $31,262 5/31/2024 $21,110 $21,752 $32,812 6/30/2024 $21,745 $21,716 $33,989 7/31/2024 $21,755 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A at NAV 8.91% 4.14% 8.73% Class A with sales charge 2.65% 2.92% 8.08% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000018475 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class C | | |
| Trading Symbol | LADCX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B44"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class C $176 1.69% | | |
| Expenses Paid, Amount | $ 176 | | |
| Expense Ratio, Percent | 1.69% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.08%, reflecting performance at the net asset value (NAV) of Class C shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B49"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class C Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,532 $10,558 $10,400 9/30/2014 $10,134 $9,992 $10,254 10/31/2014 $10,726 $10,612 $10,505 11/30/2014 $10,825 $10,681 $10,787 12/31/2014 $10,881 $10,997 $10,760 1/31/2015 $10,595 $10,746 $10,437 2/28/2015 $11,430 $11,520 $11,037 3/31/2015 $11,635 $11,727 $10,862 4/30/2015 $11,236 $11,382 $10,966 5/31/2015 $11,816 $11,800 $11,108 6/30/2015 $11,922 $11,958 $10,892 7/31/2015 $11,940 $12,007 $11,121 8/31/2015 $10,676 $11,097 $10,450 9/30/2015 $10,028 $10,396 $10,191 10/31/2015 $10,109 $10,986 $11,051 11/30/2015 $10,342 $11,389 $11,084 12/31/2015 $9,844 $10,846 $10,909 1/31/2016 $8,567 $9,670 $10,368 2/29/2016 $8,328 $9,602 $10,354 3/31/2016 $8,812 $10,338 $11,056 4/30/2016 $8,749 $10,441 $11,099 5/31/2016 $8,988 $10,722 $11,298 6/30/2016 $8,988 $10,673 $11,327 7/31/2016 $9,697 $11,371 $11,745 8/31/2016 $9,788 $11,491 $11,762 9/30/2016 $9,949 $11,657 $11,764 10/31/2016 $9,240 $10,932 $11,549 11/30/2016 $9,704 $11,911 $11,977 12/31/2016 $9,507 $12,073 $12,214 1/31/2017 $9,886 $12,269 $12,445 2/28/2017 $10,244 $12,570 $12,939 3/31/2017 $10,279 $12,719 $12,954 4/30/2017 $10,349 $12,953 $13,088 5/31/2017 $10,405 $12,835 $13,272 6/30/2017 $10,679 $13,277 $13,355 7/31/2017 $10,868 $13,390 $13,629 8/31/2017 $10,896 $13,374 $13,671 9/30/2017 $11,408 $14,103 $13,953 10/31/2017 $11,745 $14,321 $14,278 11/30/2017 $12,040 $14,732 $14,716 12/31/2017 $12,257 $14,749 $14,880 1/31/2018 $12,721 $15,324 $15,732 2/28/2018 $12,833 $14,888 $15,152 3/31/2018 $13,106 $15,088 $14,767 4/30/2018 $13,394 $15,103 $14,824 5/31/2018 $14,755 $16,054 $15,181 6/30/2018 $15,029 $16,180 $15,274 7/31/2018 $14,945 $16,458 $15,843 8/31/2018 $16,874 $17,482 $16,359 9/30/2018 $16,825 $17,073 $16,452 10/31/2018 $14,461 $14,913 $15,327 11/30/2018 $14,289 $15,146 $15,640 12/31/2018 $12,773 $13,376 $14,228 1/31/2019 $14,783 $14,921 $15,368 2/28/2019 $16,372 $15,885 $15,861 3/31/2019 $16,193 $15,670 $16,169 4/30/2019 $16,572 $16,147 $16,824 5/31/2019 $16,119 $14,949 $15,755 6/30/2019 $17,624 $16,100 $16,865 7/31/2019 $18,139 $16,258 $17,108 8/31/2019 $17,161 $15,556 $16,837 9/30/2019 $15,593 $15,428 $17,152 10/31/2019 $15,919 $15,867 $17,523 11/30/2019 $16,495 $16,801 $18,159 12/31/2019 $16,718 $17,186 $18,707 1/31/2020 $17,077 $16,997 $18,700 2/29/2020 $16,390 $15,770 $17,161 3/31/2020 $13,867 $12,758 $15,041 4/30/2020 $16,151 $14,659 $16,969 5/31/2020 $18,301 $16,044 $17,778 6/30/2020 $19,450 $16,660 $18,131 7/31/2020 $20,734 $17,233 $19,153 8/31/2020 $21,928 $18,244 $20,530 9/30/2020 $22,510 $17,853 $19,750 10/31/2020 $23,033 $17,989 $19,225 11/30/2020 $26,038 $21,161 $21,329 12/31/2020 $28,636 $23,138 $22,149 1/31/2021 $29,845 $24,254 $21,926 2/28/2021 $30,946 $25,055 $22,530 3/31/2021 $29,051 $24,267 $23,517 4/30/2021 $30,350 $24,796 $24,772 5/31/2021 $28,474 $24,087 $24,945 6/30/2021 $29,827 $25,217 $25,527 7/31/2021 $29,250 $24,299 $26,134 8/31/2021 $30,008 $24,740 $26,929 9/30/2021 $28,672 $23,792 $25,676 10/31/2021 $30,278 $24,906 $27,475 11/30/2021 $27,787 $23,689 $27,285 12/31/2021 $27,673 $23,794 $28,507 1/31/2022 $22,463 $20,605 $27,032 2/28/2022 $22,463 $20,695 $26,223 3/31/2022 $22,303 $20,790 $27,196 4/30/2022 $19,286 $18,239 $24,825 5/31/2022 $18,738 $17,895 $24,870 6/30/2022 $17,550 $16,787 $22,818 7/31/2022 $19,218 $18,666 $24,921 8/31/2022 $19,149 $18,491 $23,905 9/30/2022 $17,618 $16,827 $21,703 10/31/2022 $18,692 $18,425 $23,461 11/30/2022 $18,738 $18,725 $24,772 12/31/2022 $17,550 $17,523 $23,344 1/31/2023 $19,012 $19,266 $24,811 2/28/2023 $18,829 $19,057 $24,206 3/31/2023 $18,966 $18,587 $25,095 4/30/2023 $18,509 $18,371 $25,486 5/31/2023 $18,784 $18,374 $25,597 6/30/2023 $19,561 $19,898 $27,288 7/31/2023 $19,789 $20,828 $28,165 8/31/2023 $18,418 $19,744 $27,717 9/30/2023 $16,978 $18,442 $26,395 10/31/2023 $15,516 $17,019 $25,840 11/30/2023 $17,138 $18,569 $28,200 12/31/2023 $18,898 $20,792 $29,481 1/31/2024 $18,989 $20,125 $29,977 2/29/2024 $20,749 $21,760 $31,577 3/31/2024 $21,252 $22,369 $32,593 4/30/2024 $19,949 $20,646 $31,262 5/31/2024 $20,795 $21,752 $32,812 6/30/2024 $21,411 $21,716 $33,989 7/31/2024 $21,389 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class C at NAV 8.08% 3.35% 7.90% Class C with sales charge 7.08% 3.35% 7.90% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000054855 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class F | | |
| Trading Symbol | LADFX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B69"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class F $83 0.79% | | |
| Expenses Paid, Amount | $ 83 | | |
| Expense Ratio, Percent | 0.79% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 9.03%, reflecting performance at the net asset value (NAV) of Class F shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B74"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class F Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,542 $10,558 $10,400 9/30/2014 $10,148 $9,992 $10,254 10/31/2014 $10,750 $10,612 $10,505 11/30/2014 $10,855 $10,681 $10,787 12/31/2014 $10,922 $10,997 $10,760 1/31/2015 $10,644 $10,746 $10,437 2/28/2015 $11,487 $11,520 $11,037 3/31/2015 $11,707 $11,727 $10,862 4/30/2015 $11,309 $11,382 $10,966 5/31/2015 $11,903 $11,800 $11,108 6/30/2015 $12,018 $11,958 $10,892 7/31/2015 $12,047 $12,007 $11,121 8/31/2015 $10,778 $11,097 $10,450 9/30/2015 $10,136 $10,396 $10,191 10/31/2015 $10,223 $10,986 $11,051 11/30/2015 $10,469 $11,389 $11,084 12/31/2015 $9,972 $10,846 $10,909 1/31/2016 $8,684 $9,670 $10,368 2/29/2016 $8,448 $9,602 $10,354 3/31/2016 $8,946 $10,338 $11,056 4/30/2016 $8,888 $10,441 $11,099 5/31/2016 $9,139 $10,722 $11,298 6/30/2016 $9,144 $10,673 $11,327 7/31/2016 $9,872 $11,371 $11,745 8/31/2016 $9,977 $11,491 $11,762 9/30/2016 $10,144 $11,657 $11,764 10/31/2016 $9,427 $10,932 $11,549 11/30/2016 $9,909 $11,911 $11,977 12/31/2016 $9,715 $12,073 $12,214 1/31/2017 $10,108 $12,269 $12,445 2/28/2017 $10,485 $12,570 $12,939 3/31/2017 $10,526 $12,719 $12,954 4/30/2017 $10,610 $12,953 $13,088 5/31/2017 $10,668 $12,835 $13,272 6/30/2017 $10,961 $13,277 $13,355 7/31/2017 $11,160 $13,390 $13,629 8/31/2017 $11,202 $13,374 $13,671 9/30/2017 $11,741 $14,103 $13,953 10/31/2017 $12,097 $14,321 $14,278 11/30/2017 $12,400 $14,732 $14,716 12/31/2017 $12,641 $14,749 $14,880 1/31/2018 $13,128 $15,324 $15,732 2/28/2018 $13,254 $14,888 $15,152 3/31/2018 $13,547 $15,088 $14,767 4/30/2018 $13,850 $15,103 $14,824 5/31/2018 $15,274 $16,054 $15,181 6/30/2018 $15,583 $16,180 $15,274 7/31/2018 $15,510 $16,458 $15,843 8/31/2018 $17,525 $17,482 $16,359 9/30/2018 $17,483 $17,073 $16,452 10/31/2018 $15,038 $14,913 $15,327 11/30/2018 $14,875 $15,146 $15,640 12/31/2018 $13,300 $13,376 $14,228 1/31/2019 $15,405 $14,921 $15,368 2/28/2019 $17,083 $15,885 $15,861 3/31/2019 $16,897 $15,670 $16,169 4/30/2019 $17,317 $16,147 $16,824 5/31/2019 $16,856 $14,949 $15,755 6/30/2019 $18,444 $16,100 $16,865 7/31/2019 $18,988 $16,258 $17,108 8/31/2019 $17,984 $15,556 $16,837 9/30/2019 $16,354 $15,428 $17,152 10/31/2019 $16,711 $15,867 $17,523 11/30/2019 $17,314 $16,801 $18,159 12/31/2019 $17,575 $17,186 $18,707 1/31/2020 $17,962 $16,997 $18,700 2/29/2020 $17,255 $15,770 $17,161 3/31/2020 $14,601 $12,758 $15,041 4/30/2020 $17,027 $14,659 $16,969 5/31/2020 $19,310 $16,044 $17,778 6/30/2020 $20,541 $16,660 $18,131 7/31/2020 $21,905 $17,233 $19,153 8/31/2020 $23,178 $18,244 $20,530 9/30/2020 $23,826 $17,853 $19,750 10/31/2020 $24,399 $17,989 $19,225 11/30/2020 $27,578 $21,161 $21,329 12/31/2020 $30,371 $23,138 $22,149 1/31/2021 $31,670 $24,254 $21,926 2/28/2021 $32,867 $25,055 $22,530 3/31/2021 $30,881 $24,267 $23,517 4/30/2021 $32,273 $24,796 $24,772 5/31/2021 $30,306 $24,087 $24,945 6/30/2021 $31,781 $25,217 $25,527 7/31/2021 $31,187 $24,299 $26,134 8/31/2021 $32,013 $24,740 $26,929 9/30/2021 $30,621 $23,792 $25,676 10/31/2021 $32,347 $24,906 $27,475 11/30/2021 $29,702 $23,689 $27,285 12/31/2021 $29,599 $23,794 $28,507 1/31/2022 $24,065 $20,605 $27,032 2/28/2022 $24,075 $20,695 $26,223 3/31/2022 $23,910 $20,790 $27,196 4/30/2022 $20,710 $18,239 $24,825 5/31/2022 $20,132 $17,895 $24,870 6/30/2022 $18,862 $16,787 $22,818 7/31/2022 $20,679 $18,666 $24,921 8/31/2022 $20,627 $18,491 $23,905 9/30/2022 $18,975 $16,827 $21,703 10/31/2022 $20,152 $18,425 $23,461 11/30/2022 $20,214 $18,725 $24,772 12/31/2022 $18,955 $17,523 $23,344 1/31/2023 $20,534 $19,266 $24,811 2/28/2023 $20,348 $19,057 $24,206 3/31/2023 $20,534 $18,587 $25,095 4/30/2023 $20,028 $18,371 $25,486 5/31/2023 $20,359 $18,374 $25,597 6/30/2023 $21,205 $19,898 $27,288 7/31/2023 $21,484 $20,828 $28,165 8/31/2023 $20,018 $19,744 $27,717 9/30/2023 $18,469 $18,442 $26,395 10/31/2023 $16,890 $17,019 $25,840 11/30/2023 $18,666 $18,569 $28,200 12/31/2023 $20,586 $20,792 $29,481 1/31/2024 $20,699 $20,125 $29,977 2/29/2024 $22,630 $21,760 $31,577 3/31/2024 $23,198 $22,369 $32,593 4/30/2024 $21,794 $20,646 $31,262 5/31/2024 $22,733 $21,752 $32,812 6/30/2024 $23,425 $21,716 $33,989 7/31/2024 $23,425 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class F at NAV 9.03% 4.29% 8.88% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000188220 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class F3 | | |
| Trading Symbol | LOGWX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B94"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class F3 $62 0.59% | | |
| Expenses Paid, Amount | $ 62 | | |
| Expense Ratio, Percent | 0.59% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 9.29%, reflecting performance at the net asset value (NAV) of Class F3 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B99"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class F3 Russell 2000 Growth Index S&P 500 Index 4/4/2017 $10,000 $10,000 $10,000 4/30/2017 $10,158 $10,333 $10,112 5/31/2017 $10,217 $10,239 $10,254 6/30/2017 $10,498 $10,591 $10,318 7/31/2017 $10,693 $10,681 $10,530 8/31/2017 $10,733 $10,669 $10,562 9/30/2017 $11,249 $11,250 $10,780 10/31/2017 $11,593 $11,424 $11,032 11/30/2017 $11,892 $11,752 $11,370 12/31/2017 $12,119 $11,765 $11,496 1/31/2018 $12,589 $12,224 $12,155 2/28/2018 $12,712 $11,876 $11,707 3/31/2018 $12,997 $12,036 $11,409 4/30/2018 $13,287 $12,048 $11,453 5/31/2018 $14,658 $12,806 $11,729 6/30/2018 $14,957 $12,906 $11,801 7/31/2018 $14,889 $13,128 $12,240 8/31/2018 $16,827 $13,946 $12,639 9/30/2018 $16,790 $13,619 $12,711 10/31/2018 $14,441 $11,896 $11,842 11/30/2018 $14,286 $12,082 $12,083 12/31/2018 $12,781 $10,670 $10,992 1/31/2019 $14,799 $11,902 $11,873 2/28/2019 $16,414 $12,671 $12,254 3/31/2019 $16,241 $12,500 $12,493 4/30/2019 $16,645 $12,880 $12,998 5/31/2019 $16,207 $11,925 $12,172 6/30/2019 $17,735 $12,843 $13,030 7/31/2019 $18,260 $12,969 $13,218 8/31/2019 $17,302 $12,409 $13,008 9/30/2019 $15,734 $12,307 $13,252 10/31/2019 $16,080 $12,657 $13,539 11/30/2019 $16,667 $13,402 $14,030 12/31/2019 $16,921 $13,709 $14,453 1/31/2020 $17,292 $13,559 $14,448 2/29/2020 $16,619 $12,580 $13,258 3/31/2020 $14,064 $10,177 $11,621 4/30/2020 $16,399 $11,693 $13,111 5/31/2020 $18,603 $12,798 $13,735 6/30/2020 $19,791 $13,290 $14,008 7/31/2020 $21,110 $13,747 $14,798 8/31/2020 $22,339 $14,553 $15,862 9/30/2020 $22,964 $14,241 $15,259 10/31/2020 $23,520 $14,349 $14,853 11/30/2020 $26,592 $16,880 $16,479 12/31/2020 $29,280 $18,457 $17,113 1/31/2021 $30,538 $19,347 $16,940 2/28/2021 $31,693 $19,986 $17,407 3/31/2021 $29,786 $19,357 $18,169 4/30/2021 $31,134 $19,779 $19,139 5/31/2021 $29,250 $19,214 $19,273 6/30/2021 $30,672 $20,116 $19,723 7/31/2021 $30,106 $19,383 $20,191 8/31/2021 $30,911 $19,735 $20,805 9/30/2021 $29,570 $18,978 $19,838 10/31/2021 $31,238 $19,867 $21,227 11/30/2021 $28,691 $18,897 $21,080 12/31/2021 $28,602 $18,981 $22,025 1/31/2022 $23,252 $16,437 $20,885 2/28/2022 $23,277 $16,508 $20,260 3/31/2022 $23,114 $16,584 $21,012 4/30/2022 $20,025 $14,549 $19,180 5/31/2022 $19,464 $14,274 $19,215 6/30/2022 $18,244 $13,391 $17,629 7/31/2022 $20,000 $14,890 $19,254 8/31/2022 $19,951 $14,750 $18,469 9/30/2022 $18,366 $13,423 $16,768 10/31/2022 $19,504 $14,697 $18,126 11/30/2022 $19,569 $14,937 $19,139 12/31/2022 $18,350 $13,978 $18,036 1/31/2023 $19,886 $15,368 $19,169 2/28/2023 $19,708 $15,202 $18,702 3/31/2023 $19,886 $14,827 $19,388 4/30/2023 $19,407 $14,654 $19,691 5/31/2023 $19,732 $14,657 $19,777 6/30/2023 $20,553 $15,872 $21,083 7/31/2023 $20,821 $16,614 $21,761 8/31/2023 $19,399 $15,749 $21,414 9/30/2023 $17,903 $14,711 $20,393 10/31/2023 $16,382 $13,576 $19,964 11/30/2023 $18,106 $14,812 $21,788 12/31/2023 $19,968 $16,586 $22,777 1/31/2024 $20,082 $16,054 $23,160 2/29/2024 $21,960 $17,358 $24,397 3/31/2024 $22,512 $17,843 $25,182 4/30/2024 $21,155 $16,469 $24,153 5/31/2024 $22,065 $17,351 $25,351 6/30/2024 $22,748 $17,322 $26,260 7/31/2024 $22,756 $18,741 $26,580 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Since Inception
4/4/17 Class F3 at NAV 9.29% 4.50% 11.88% Russell 2000 Growth Index 12.80% 7.64% 8.96% S&P 500 Index Footnote Reference 22.15% 15.00% 14.28% | | |
| Performance Inception Date | | Apr. 04, 2017 | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000018477 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class I | | |
| Trading Symbol | LADYX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B120"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class I $72 0.69% | | |
| Expenses Paid, Amount | $ 72 | | |
| Expense Ratio, Percent | 0.69% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 9.17%, reflecting performance at the net asset value (NAV) of Class I shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B125"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class I Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,544 $10,558 $10,400 9/30/2014 $10,149 $9,992 $10,254 10/31/2014 $10,756 $10,612 $10,505 11/30/2014 $10,861 $10,681 $10,787 12/31/2014 $10,927 $10,997 $10,760 1/31/2015 $10,646 $10,746 $10,437 2/28/2015 $11,496 $11,520 $11,037 3/31/2015 $11,711 $11,727 $10,862 4/30/2015 $11,321 $11,382 $10,966 5/31/2015 $11,908 $11,800 $11,108 6/30/2015 $12,027 $11,958 $10,892 7/31/2015 $12,057 $12,007 $11,121 8/31/2015 $10,791 $11,097 $10,450 9/30/2015 $10,146 $10,396 $10,191 10/31/2015 $10,234 $10,986 $11,051 11/30/2015 $10,482 $11,389 $11,084 12/31/2015 $9,983 $10,846 $10,909 1/31/2016 $8,694 $9,670 $10,368 2/29/2016 $8,466 $9,602 $10,354 3/31/2016 $8,961 $10,338 $11,056 4/30/2016 $8,904 $10,441 $11,099 5/31/2016 $9,155 $10,722 $11,298 6/30/2016 $9,165 $10,673 $11,327 7/31/2016 $9,892 $11,371 $11,745 8/31/2016 $9,997 $11,491 $11,762 9/30/2016 $10,168 $11,657 $11,764 10/31/2016 $9,450 $10,932 $11,549 11/30/2016 $9,930 $11,911 $11,977 12/31/2016 $9,735 $12,073 $12,214 1/31/2017 $10,135 $12,269 $12,445 2/28/2017 $10,510 $12,570 $12,939 3/31/2017 $10,558 $12,719 $12,954 4/30/2017 $10,639 $12,953 $13,088 5/31/2017 $10,700 $12,835 $13,272 6/30/2017 $10,990 $13,277 $13,355 7/31/2017 $11,195 $13,390 $13,629 8/31/2017 $11,233 $13,374 $13,671 9/30/2017 $11,779 $14,103 $13,953 10/31/2017 $12,136 $14,321 $14,278 11/30/2017 $12,445 $14,732 $14,716 12/31/2017 $12,683 $14,749 $14,880 1/31/2018 $13,172 $15,324 $15,732 2/28/2018 $13,301 $14,888 $15,152 3/31/2018 $13,595 $15,088 $14,767 4/30/2018 $13,900 $15,103 $14,824 5/31/2018 $15,335 $16,054 $15,181 6/30/2018 $15,644 $16,180 $15,274 7/31/2018 $15,573 $16,458 $15,843 8/31/2018 $17,598 $17,482 $16,359 9/30/2018 $17,560 $17,073 $16,452 10/31/2018 $15,102 $14,913 $15,327 11/30/2018 $14,940 $15,146 $15,640 12/31/2018 $13,363 $13,376 $14,228 1/31/2019 $15,473 $14,921 $15,368 2/28/2019 $17,159 $15,885 $15,861 3/31/2019 $16,977 $15,670 $16,169 4/30/2019 $17,395 $16,147 $16,824 5/31/2019 $16,940 $14,949 $15,755 6/30/2019 $18,535 $16,100 $16,865 7/31/2019 $19,087 $16,258 $17,108 8/31/2019 $18,080 $15,556 $16,837 9/30/2019 $16,443 $15,428 $17,152 10/31/2019 $16,801 $15,867 $17,523 11/30/2019 $17,413 $16,801 $18,159 12/31/2019 $17,673 $17,186 $18,707 1/31/2020 $18,063 $16,997 $18,700 2/29/2020 $17,355 $15,770 $17,161 3/31/2020 $14,688 $12,758 $15,041 4/30/2020 $17,131 $14,659 $16,969 5/31/2020 $19,429 $16,044 $17,778 6/30/2020 $20,665 $16,660 $18,131 7/31/2020 $22,046 $17,233 $19,153 8/31/2020 $23,325 $18,244 $20,530 9/30/2020 $23,969 $17,853 $19,750 10/31/2020 $24,554 $17,989 $19,225 11/30/2020 $27,758 $21,161 $21,329 12/31/2020 $30,566 $23,138 $22,149 1/31/2021 $31,876 $24,254 $21,926 2/28/2021 $33,084 $25,055 $22,530 3/31/2021 $31,091 $24,267 $23,517 4/30/2021 $32,495 $24,796 $24,772 5/31/2021 $30,519 $24,087 $24,945 6/30/2021 $32,001 $25,217 $25,527 7/31/2021 $31,405 $24,299 $26,134 8/31/2021 $32,237 $24,740 $26,929 9/30/2021 $30,840 $23,792 $25,676 10/31/2021 $32,582 $24,906 $27,475 11/30/2021 $29,922 $23,689 $27,285 12/31/2021 $29,828 $23,794 $28,507 1/31/2022 $24,248 $20,605 $27,032 2/28/2022 $24,265 $20,695 $26,223 3/31/2022 $24,094 $20,790 $27,196 4/30/2022 $20,871 $18,239 $24,825 5/31/2022 $20,288 $17,895 $24,870 6/30/2022 $19,011 $16,787 $22,818 7/31/2022 $20,845 $18,666 $24,921 8/31/2022 $20,794 $18,491 $23,905 9/30/2022 $19,140 $16,827 $21,703 10/31/2022 $20,314 $18,425 $23,461 11/30/2022 $20,382 $18,725 $24,772 12/31/2022 $19,114 $17,523 $23,344 1/31/2023 $20,717 $19,266 $24,811 2/28/2023 $20,528 $19,057 $24,206 3/31/2023 $20,717 $18,587 $25,095 4/30/2023 $20,211 $18,371 $25,486 5/31/2023 $20,545 $18,374 $25,597 6/30/2023 $21,402 $19,898 $27,288 7/31/2023 $21,677 $20,828 $28,165 8/31/2023 $20,202 $19,744 $27,717 9/30/2023 $18,634 $18,442 $26,395 10/31/2023 $17,048 $17,019 $25,840 11/30/2023 $18,840 $18,569 $28,200 12/31/2023 $20,785 $20,792 $29,481 1/31/2024 $20,897 $20,125 $29,977 2/29/2024 $22,851 $21,760 $31,577 3/31/2024 $23,425 $22,369 $32,593 4/30/2024 $22,011 $20,646 $31,262 5/31/2024 $22,954 $21,752 $32,812 6/30/2024 $23,657 $21,716 $33,989 7/31/2024 $23,665 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class I at NAV 9.17% 4.39% 9.00% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000018476 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class P | | |
| Trading Symbol | LADPX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B145"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class P $119 1.14% | | |
| Expenses Paid, Amount | $ 119 | | |
| Expense Ratio, Percent | 1.14% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.67%, reflecting performance at the net asset value (NAV) of Class P shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B150"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class P Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,542 $10,558 $10,400 9/30/2014 $10,147 $9,992 $10,254 10/31/2014 $10,748 $10,612 $10,505 11/30/2014 $10,853 $10,681 $10,787 12/31/2014 $10,913 $10,997 $10,760 1/31/2015 $10,635 $10,746 $10,437 2/28/2015 $11,475 $11,520 $11,037 3/31/2015 $11,692 $11,727 $10,862 4/30/2015 $11,298 $11,382 $10,966 5/31/2015 $11,884 $11,800 $11,108 6/30/2015 $12,001 $11,958 $10,892 7/31/2015 $12,026 $12,007 $11,121 8/31/2015 $10,762 $11,097 $10,450 9/30/2015 $10,119 $10,396 $10,191 10/31/2015 $10,200 $10,986 $11,051 11/30/2015 $10,445 $11,389 $11,084 12/31/2015 $9,945 $10,846 $10,909 1/31/2016 $8,661 $9,670 $10,368 2/29/2016 $8,427 $9,602 $10,354 3/31/2016 $8,922 $10,338 $11,056 4/30/2016 $8,861 $10,441 $11,099 5/31/2016 $9,111 $10,722 $11,298 6/30/2016 $9,122 $10,673 $11,327 7/31/2016 $9,839 $11,371 $11,745 8/31/2016 $9,945 $11,491 $11,762 9/30/2016 $10,112 $11,657 $11,764 10/31/2016 $9,394 $10,932 $11,549 11/30/2016 $9,873 $11,911 $11,977 12/31/2016 $9,678 $12,073 $12,214 1/31/2017 $10,073 $12,269 $12,445 2/28/2017 $10,440 $12,570 $12,939 3/31/2017 $10,484 $12,719 $12,954 4/30/2017 $10,567 $12,953 $13,088 5/31/2017 $10,623 $12,835 $13,272 6/30/2017 $10,912 $13,277 $13,355 7/31/2017 $11,112 $13,390 $13,629 8/31/2017 $11,146 $13,374 $13,671 9/30/2017 $11,685 $14,103 $13,953 10/31/2017 $12,035 $14,321 $14,278 11/30/2017 $12,341 $14,732 $14,716 12/31/2017 $12,574 $14,749 $14,880 1/31/2018 $13,058 $15,324 $15,732 2/28/2018 $13,180 $14,888 $15,152 3/31/2018 $13,469 $15,088 $14,767 4/30/2018 $13,769 $15,103 $14,824 5/31/2018 $15,187 $16,054 $15,181 6/30/2018 $15,487 $16,180 $15,274 7/31/2018 $15,409 $16,458 $15,843 8/31/2018 $17,410 $17,482 $16,359 9/30/2018 $17,360 $17,073 $16,452 10/31/2018 $14,926 $14,913 $15,327 11/30/2018 $14,763 $15,146 $15,640 12/31/2018 $13,195 $13,376 $14,228 1/31/2019 $15,278 $14,921 $15,368 2/28/2019 $16,936 $15,885 $15,861 3/31/2019 $16,749 $15,670 $16,169 4/30/2019 $17,160 $16,147 $16,824 5/31/2019 $16,705 $14,949 $15,755 6/30/2019 $18,265 $16,100 $16,865 7/31/2019 $18,803 $16,258 $17,108 8/31/2019 $17,802 $15,556 $16,837 9/30/2019 $16,189 $15,428 $17,152 10/31/2019 $16,533 $15,867 $17,523 11/30/2019 $17,128 $16,801 $18,159 12/31/2019 $17,381 $17,186 $18,707 1/31/2020 $17,755 $16,997 $18,700 2/29/2020 $17,053 $15,770 $17,161 3/31/2020 $14,425 $12,758 $15,041 4/30/2020 $16,820 $14,659 $16,969 5/31/2020 $19,065 $16,044 $17,778 6/30/2020 $20,271 $16,660 $18,131 7/31/2020 $21,619 $17,233 $19,153 8/31/2020 $22,863 $18,244 $20,530 9/30/2020 $23,489 $17,853 $19,750 10/31/2020 $24,051 $17,989 $19,225 11/30/2020 $27,187 $21,161 $21,329 12/31/2020 $29,921 $23,138 $22,149 1/31/2021 $31,195 $24,254 $21,926 2/28/2021 $32,363 $25,055 $22,530 3/31/2021 $30,401 $24,267 $23,517 4/30/2021 $31,758 $24,796 $24,772 5/31/2021 $29,817 $24,087 $24,945 6/30/2021 $31,257 $25,217 $25,527 7/31/2021 $30,662 $24,299 $26,134 8/31/2021 $31,466 $24,740 $26,929 9/30/2021 $30,088 $23,792 $25,676 10/31/2021 $31,769 $24,906 $27,475 11/30/2021 $29,169 $23,689 $27,285 12/31/2021 $29,063 $23,794 $28,507 1/31/2022 $23,621 $20,605 $27,032 2/28/2022 $23,621 $20,695 $26,223 3/31/2022 $23,456 $20,790 $27,196 4/30/2022 $20,304 $18,239 $24,825 5/31/2022 $19,737 $17,895 $24,870 6/30/2022 $18,486 $16,787 $22,818 7/31/2022 $20,257 $18,666 $24,921 8/31/2022 $20,198 $18,491 $23,905 9/30/2022 $18,581 $16,827 $21,703 10/31/2022 $19,726 $18,425 $23,461 11/30/2022 $19,785 $18,725 $24,772 12/31/2022 $18,545 $17,523 $23,344 1/31/2023 $20,092 $19,266 $24,811 2/28/2023 $19,903 $19,057 $24,206 3/31/2023 $20,068 $18,587 $25,095 4/30/2023 $19,572 $18,371 $25,486 5/31/2023 $19,891 $18,374 $25,597 6/30/2023 $20,717 $19,898 $27,288 7/31/2023 $20,977 $20,828 $28,165 8/31/2023 $19,537 $19,744 $27,717 9/30/2023 $18,014 $18,442 $26,395 10/31/2023 $16,479 $17,019 $25,840 11/30/2023 $18,203 $18,569 $28,200 12/31/2023 $20,068 $20,792 $29,481 1/31/2024 $20,174 $20,125 $29,977 2/29/2024 $22,051 $21,760 $31,577 3/31/2024 $22,594 $22,369 $32,593 4/30/2024 $21,225 $20,646 $31,262 5/31/2024 $22,122 $21,752 $32,812 6/30/2024 $22,795 $21,716 $33,989 7/31/2024 $22,795 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class P at NAV 8.67% 3.93% 8.59% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000054856 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class R2 | | |
| Trading Symbol | LADQX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B170"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R2 $134 1.29% | | |
| Expenses Paid, Amount | $ 134 | | |
| Expense Ratio, Percent | 1.29% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.49%, reflecting performance at the net asset value (NAV) of Class R2 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B175"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class R2 Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,538 $10,558 $10,400 9/30/2014 $10,143 $9,992 $10,254 10/31/2014 $10,739 $10,612 $10,505 11/30/2014 $10,840 $10,681 $10,787 12/31/2014 $10,906 $10,997 $10,760 1/31/2015 $10,617 $10,746 $10,437 2/28/2015 $11,457 $11,520 $11,037 3/31/2015 $11,670 $11,727 $10,862 4/30/2015 $11,270 $11,382 $10,966 5/31/2015 $11,852 $11,800 $11,108 6/30/2015 $11,968 $11,958 $10,892 7/31/2015 $11,988 $12,007 $11,121 8/31/2015 $10,724 $11,097 $10,450 9/30/2015 $10,081 $10,396 $10,191 10/31/2015 $10,162 $10,986 $11,051 11/30/2015 $10,402 $11,389 $11,084 12/31/2015 $9,901 $10,846 $10,909 1/31/2016 $8,617 $9,670 $10,368 2/29/2016 $8,383 $9,602 $10,354 3/31/2016 $8,872 $10,338 $11,056 4/30/2016 $8,811 $10,441 $11,099 5/31/2016 $9,056 $10,722 $11,298 6/30/2016 $9,062 $10,673 $11,327 7/31/2016 $9,774 $11,371 $11,745 8/31/2016 $9,874 $11,491 $11,762 9/30/2016 $10,041 $11,657 $11,764 10/31/2016 $9,323 $10,932 $11,549 11/30/2016 $9,796 $11,911 $11,977 12/31/2016 $9,601 $12,073 $12,214 1/31/2017 $9,985 $12,269 $12,445 2/28/2017 $10,352 $12,570 $12,939 3/31/2017 $10,391 $12,719 $12,954 4/30/2017 $10,469 $12,953 $13,088 5/31/2017 $10,525 $12,835 $13,272 6/30/2017 $10,803 $13,277 $13,355 7/31/2017 $10,997 $13,390 $13,629 8/31/2017 $11,031 $13,374 $13,671 9/30/2017 $11,559 $14,103 $13,953 10/31/2017 $11,904 $14,321 $14,278 11/30/2017 $12,199 $14,732 $14,716 12/31/2017 $12,427 $14,749 $14,880 1/31/2018 $12,900 $15,324 $15,732 2/28/2018 $13,022 $14,888 $15,152 3/31/2018 $13,306 $15,088 $14,767 4/30/2018 $13,595 $15,103 $14,824 5/31/2018 $14,986 $16,054 $15,181 6/30/2018 $15,281 $16,180 $15,274 7/31/2018 $15,203 $16,458 $15,843 8/31/2018 $17,172 $17,482 $16,359 9/30/2018 $17,127 $17,073 $16,452 10/31/2018 $14,724 $14,913 $15,327 11/30/2018 $14,554 $15,146 $15,640 12/31/2018 $13,015 $13,376 $14,228 1/31/2019 $15,065 $14,921 $15,368 2/28/2019 $16,695 $15,885 $15,861 3/31/2019 $16,514 $15,670 $16,169 4/30/2019 $16,912 $16,147 $16,824 5/31/2019 $16,462 $14,949 $15,755 6/30/2019 $18,001 $16,100 $16,865 7/31/2019 $18,527 $16,258 $17,108 8/31/2019 $17,536 $15,556 $16,837 9/30/2019 $15,944 $15,428 $17,152 10/31/2019 $16,282 $15,867 $17,523 11/30/2019 $16,864 $16,801 $18,159 12/31/2019 $17,110 $17,186 $18,707 1/31/2020 $17,479 $16,997 $18,700 2/29/2020 $16,789 $15,770 $17,161 3/31/2020 $14,197 $12,758 $15,041 4/30/2020 $16,552 $14,659 $16,969 5/31/2020 $18,756 $16,044 $17,778 6/30/2020 $19,948 $16,660 $18,131 7/31/2020 $21,262 $17,233 $19,153 8/31/2020 $22,492 $18,244 $20,530 9/30/2020 $23,107 $17,853 $19,750 10/31/2020 $23,646 $17,989 $19,225 11/30/2020 $26,722 $21,161 $21,329 12/31/2020 $29,411 $23,138 $22,149 1/31/2021 $30,660 $24,254 $21,926 2/28/2021 $31,804 $25,055 $22,530 3/31/2021 $29,877 $24,267 $23,517 4/30/2021 $31,211 $24,796 $24,772 5/31/2021 $29,294 $24,087 $24,945 6/30/2021 $30,703 $25,217 $25,527 7/31/2021 $30,120 $24,299 $26,134 8/31/2021 $30,904 $24,740 $26,929 9/30/2021 $29,549 $23,792 $25,676 10/31/2021 $31,200 $24,906 $27,475 11/30/2021 $28,637 $23,689 $27,285 12/31/2021 $28,528 $23,794 $28,507 1/31/2022 $23,176 $20,605 $27,032 2/28/2022 $23,188 $20,695 $26,223 3/31/2022 $23,008 $20,790 $27,196 4/30/2022 $19,929 $18,239 $24,825 5/31/2022 $19,364 $17,895 $24,870 6/30/2022 $18,137 $16,787 $22,818 7/31/2022 $19,869 $18,666 $24,921 8/31/2022 $19,809 $18,491 $23,905 9/30/2022 $18,221 $16,827 $21,703 10/31/2022 $19,340 $18,425 $23,461 11/30/2022 $19,400 $18,725 $24,772 12/31/2022 $18,173 $17,523 $23,344 1/31/2023 $19,688 $19,266 $24,811 2/28/2023 $19,496 $19,057 $24,206 3/31/2023 $19,664 $18,587 $25,095 4/30/2023 $19,183 $18,371 $25,486 5/31/2023 $19,484 $18,374 $25,597 6/30/2023 $20,290 $19,898 $27,288 7/31/2023 $20,542 $20,828 $28,165 8/31/2023 $19,135 $19,744 $27,717 9/30/2023 $17,644 $18,442 $26,395 10/31/2023 $16,128 $17,019 $25,840 11/30/2023 $17,812 $18,569 $28,200 12/31/2023 $19,640 $20,792 $29,481 1/31/2024 $19,737 $20,125 $29,977 2/29/2024 $21,577 $21,760 $31,577 3/31/2024 $22,106 $22,369 $32,593 4/30/2024 $20,759 $20,646 $31,262 5/31/2024 $21,649 $21,752 $32,812 6/30/2024 $22,298 $21,716 $33,989 7/31/2024 $22,286 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class R2 at NAV 8.49% 3.76% 8.34% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000054857 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class R3 | | |
| Trading Symbol | LADRX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B195"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R3 $124 1.19% | | |
| Expenses Paid, Amount | $ 124 | | |
| Expense Ratio, Percent | 1.19% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.65%, reflecting performance at the net asset value (NAV) of Class R3 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B200"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class R3 Russell 2000 Growth Index S&P 500 Index 7/31/2014 $10,000 $10,000 $10,000 8/31/2014 $10,537 $10,558 $10,400 9/30/2014 $10,141 $9,992 $10,254 10/31/2014 $10,740 $10,612 $10,505 11/30/2014 $10,840 $10,681 $10,787 12/31/2014 $10,905 $10,997 $10,760 1/31/2015 $10,620 $10,746 $10,437 2/28/2015 $11,460 $11,520 $11,037 3/31/2015 $11,675 $11,727 $10,862 4/30/2015 $11,275 $11,382 $10,966 5/31/2015 $11,860 $11,800 $11,108 6/30/2015 $11,975 $11,958 $10,892 7/31/2015 $11,995 $12,007 $11,121 8/31/2015 $10,730 $11,097 $10,450 9/30/2015 $10,090 $10,396 $10,191 10/31/2015 $10,170 $10,986 $11,051 11/30/2015 $10,412 $11,389 $11,084 12/31/2015 $9,913 $10,846 $10,909 1/31/2016 $8,628 $9,670 $10,368 2/29/2016 $8,397 $9,602 $10,354 3/31/2016 $8,886 $10,338 $11,056 4/30/2016 $8,825 $10,441 $11,099 5/31/2016 $9,072 $10,722 $11,298 6/30/2016 $9,078 $10,673 $11,327 7/31/2016 $9,792 $11,371 $11,745 8/31/2016 $9,891 $11,491 $11,762 9/30/2016 $10,056 $11,657 $11,764 10/31/2016 $9,342 $10,932 $11,549 11/30/2016 $9,814 $11,911 $11,977 12/31/2016 $9,616 $12,073 $12,214 1/31/2017 $10,006 $12,269 $12,445 2/28/2017 $10,374 $12,570 $12,939 3/31/2017 $10,412 $12,719 $12,954 4/30/2017 $10,489 $12,953 $13,088 5/31/2017 $10,550 $12,835 $13,272 6/30/2017 $10,830 $13,277 $13,355 7/31/2017 $11,028 $13,390 $13,629 8/31/2017 $11,061 $13,374 $13,671 9/30/2017 $11,588 $14,103 $13,953 10/31/2017 $11,939 $14,321 $14,278 11/30/2017 $12,236 $14,732 $14,716 12/31/2017 $12,466 $14,749 $14,880 1/31/2018 $12,939 $15,324 $15,732 2/28/2018 $13,060 $14,888 $15,152 3/31/2018 $13,345 $15,088 $14,767 4/30/2018 $13,642 $15,103 $14,824 5/31/2018 $15,042 $16,054 $15,181 6/30/2018 $15,339 $16,180 $15,274 7/31/2018 $15,262 $16,458 $15,843 8/31/2018 $17,239 $17,482 $16,359 9/30/2018 $17,195 $17,073 $16,452 10/31/2018 $14,778 $14,913 $15,327 11/30/2018 $14,612 $15,146 $15,640 12/31/2018 $13,063 $13,376 $14,228 1/31/2019 $15,128 $14,921 $15,368 2/28/2019 $16,764 $15,885 $15,861 3/31/2019 $16,580 $15,670 $16,169 4/30/2019 $16,985 $16,147 $16,824 5/31/2019 $16,536 $14,949 $15,755 6/30/2019 $18,084 $16,100 $16,865 7/31/2019 $18,607 $16,258 $17,108 8/31/2019 $17,619 $15,556 $16,837 9/30/2019 $16,020 $15,428 $17,152 10/31/2019 $16,359 $15,867 $17,523 11/30/2019 $16,946 $16,801 $18,159 12/31/2019 $17,196 $17,186 $18,707 1/31/2020 $17,565 $16,997 $18,700 2/29/2020 $16,873 $15,770 $17,161 3/31/2020 $14,270 $12,758 $15,041 4/30/2020 $16,642 $14,659 $16,969 5/31/2020 $18,866 $16,044 $17,778 6/30/2020 $20,057 $16,660 $18,131 7/31/2020 $21,386 $17,233 $19,153 8/31/2020 $22,623 $18,244 $20,530 9/30/2020 $23,241 $17,853 $19,750 10/31/2020 $23,795 $17,989 $19,225 11/30/2020 $26,889 $21,161 $21,329 12/31/2020 $29,597 $23,138 $22,149 1/31/2021 $30,853 $24,254 $21,926 2/28/2021 $32,006 $25,055 $22,530 3/31/2021 $30,060 $24,267 $23,517 4/30/2021 $31,409 $24,796 $24,772 5/31/2021 $29,494 $24,087 $24,945 6/30/2021 $30,904 $25,217 $25,527 7/31/2021 $30,318 $24,299 $26,134 8/31/2021 $31,110 $24,740 $26,929 9/30/2021 $29,751 $23,792 $25,676 10/31/2021 $31,419 $24,906 $27,475 11/30/2021 $28,834 $23,689 $27,285 12/31/2021 $28,729 $23,794 $28,507 1/31/2022 $23,351 $20,605 $27,032 2/28/2022 $23,363 $20,695 $26,223 3/31/2022 $23,188 $20,790 $27,196 4/30/2022 $20,080 $18,239 $24,825 5/31/2022 $19,510 $17,895 $24,870 6/30/2022 $18,276 $16,787 $22,818 7/31/2022 $20,022 $18,666 $24,921 8/31/2022 $19,964 $18,491 $23,905 9/30/2022 $18,369 $16,827 $21,703 10/31/2022 $19,498 $18,425 $23,461 11/30/2022 $19,556 $18,725 $24,772 12/31/2022 $18,322 $17,523 $23,344 1/31/2023 $19,847 $19,266 $24,811 2/28/2023 $19,661 $19,057 $24,206 3/31/2023 $19,836 $18,587 $25,095 4/30/2023 $19,347 $18,371 $25,486 5/31/2023 $19,649 $18,374 $25,597 6/30/2023 $20,464 $19,898 $27,288 7/31/2023 $20,720 $20,828 $28,165 8/31/2023 $19,300 $19,744 $27,717 9/30/2023 $17,798 $18,442 $26,395 10/31/2023 $16,274 $17,019 $25,840 11/30/2023 $17,985 $18,569 $28,200 12/31/2023 $19,824 $20,792 $29,481 1/31/2024 $19,929 $20,125 $29,977 2/29/2024 $21,780 $21,760 $31,577 3/31/2024 $22,315 $22,369 $32,593 4/30/2024 $20,965 $20,646 $31,262 5/31/2024 $21,849 $21,752 $32,812 6/30/2024 $22,513 $21,716 $33,989 7/31/2024 $22,513 $23,493 $34,403 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class R3 at NAV 8.65% 3.88% 8.45% Russell 2000 Growth Index 12.80% 7.64% 8.92% S&P 500 Index Footnote Reference 22.15% 15.00% 13.15% | | |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000151972 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class R4 | | |
| Trading Symbol | LADSX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B220"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R4 $98 0.94% | | |
| Expenses Paid, Amount | $ 98 | | |
| Expense Ratio, Percent | 0.94% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 8.91%, reflecting performance at the net asset value (NAV) of Class R4 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B225"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class R4 Russell 2000 Growth Index S&P 500 Index 6/30/2015 $10,000 $10,000 $10,000 7/31/2015 $10,020 $10,041 $10,210 8/31/2015 $8,967 $9,280 $9,594 9/30/2015 $8,430 $8,694 $9,356 10/31/2015 $8,500 $9,187 $10,145 11/30/2015 $8,707 $9,524 $10,176 12/31/2015 $8,289 $9,069 $10,015 1/31/2016 $7,220 $8,087 $9,518 2/29/2016 $7,027 $8,030 $9,505 3/31/2016 $7,435 $8,645 $10,150 4/30/2016 $7,386 $8,731 $10,189 5/31/2016 $7,593 $8,966 $10,372 6/30/2016 $7,597 $8,925 $10,399 7/31/2016 $8,199 $9,508 $10,783 8/31/2016 $8,285 $9,609 $10,798 9/30/2016 $8,424 $9,748 $10,800 10/31/2016 $7,831 $9,142 $10,603 11/30/2016 $8,226 $9,960 $10,996 12/31/2016 $8,064 $10,096 $11,213 1/31/2017 $8,392 $10,260 $11,426 2/28/2017 $8,702 $10,511 $11,879 3/31/2017 $8,734 $10,636 $11,893 4/30/2017 $8,801 $10,832 $12,015 5/31/2017 $8,851 $10,733 $12,184 6/30/2017 $9,089 $11,103 $12,260 7/31/2017 $9,255 $11,197 $12,512 8/31/2017 $9,286 $11,184 $12,551 9/30/2017 $9,736 $11,793 $12,810 10/31/2017 $10,028 $11,976 $13,109 11/30/2017 $10,279 $12,320 $13,511 12/31/2017 $10,477 $12,334 $13,661 1/31/2018 $10,877 $12,815 $14,443 2/28/2018 $10,980 $12,450 $13,911 3/31/2018 $11,223 $12,617 $13,557 4/30/2018 $11,474 $12,630 $13,609 5/31/2018 $12,651 $13,425 $13,937 6/30/2018 $12,908 $13,530 $14,023 7/31/2018 $12,845 $13,763 $14,544 8/31/2018 $14,511 $14,619 $15,018 9/30/2018 $14,476 $14,277 $15,104 10/31/2018 $12,449 $12,471 $14,072 11/30/2018 $12,314 $12,666 $14,358 12/31/2018 $11,006 $11,186 $13,062 1/31/2019 $12,750 $12,478 $14,109 2/28/2019 $14,135 $13,283 $14,562 3/31/2019 $13,980 $13,104 $14,845 4/30/2019 $14,320 $13,503 $15,446 5/31/2019 $13,944 $12,501 $14,464 6/30/2019 $15,252 $13,464 $15,483 7/31/2019 $15,700 $13,595 $15,706 8/31/2019 $14,870 $13,009 $15,457 9/30/2019 $13,520 $12,902 $15,746 10/31/2019 $13,813 $13,269 $16,087 11/30/2019 $14,313 $14,050 $16,671 12/31/2019 $14,527 $14,372 $17,175 1/31/2020 $14,838 $14,214 $17,168 2/29/2020 $14,261 $13,187 $15,755 3/31/2020 $12,063 $10,669 $13,809 4/30/2020 $14,068 $12,258 $15,579 5/31/2020 $15,948 $13,416 $16,321 6/30/2020 $16,962 $13,932 $16,645 7/31/2020 $18,087 $14,411 $17,584 8/31/2020 $19,138 $15,256 $18,848 9/30/2020 $19,663 $14,929 $18,132 10/31/2020 $20,137 $15,043 $17,650 11/30/2020 $22,767 $17,695 $19,582 12/31/2020 $25,056 $19,349 $20,335 1/31/2021 $26,130 $20,282 $20,129 2/28/2021 $27,115 $20,952 $20,684 3/31/2021 $25,474 $20,292 $21,590 4/30/2021 $26,614 $20,735 $22,742 5/31/2021 $24,998 $20,143 $22,901 6/30/2021 $26,204 $21,087 $23,436 7/31/2021 $25,712 $20,319 $23,993 8/31/2021 $26,385 $20,689 $24,722 9/30/2021 $25,236 $19,895 $23,572 10/31/2021 $26,655 $20,827 $25,224 11/30/2021 $24,472 $19,810 $25,049 12/31/2021 $24,389 $19,898 $26,172 1/31/2022 $19,824 $17,231 $24,817 2/28/2022 $19,833 $17,306 $24,074 3/31/2022 $19,695 $17,385 $24,968 4/30/2022 $17,054 $15,252 $22,791 5/31/2022 $16,575 $14,964 $22,833 6/30/2022 $15,526 $14,038 $20,948 7/31/2022 $17,017 $15,609 $22,879 8/31/2022 $16,971 $15,463 $21,946 9/30/2022 $15,618 $14,072 $19,925 10/31/2022 $16,584 $15,407 $21,538 11/30/2022 $16,630 $15,658 $22,742 12/31/2022 $15,590 $14,653 $21,432 1/31/2023 $16,897 $16,111 $22,778 2/28/2023 $16,741 $15,936 $22,223 3/31/2023 $16,888 $15,543 $23,038 4/30/2023 $16,474 $15,362 $23,398 5/31/2023 $16,741 $15,365 $23,500 6/30/2023 $17,440 $16,639 $25,053 7/31/2023 $17,661 $17,417 $25,857 8/31/2023 $16,456 $16,510 $25,446 9/30/2023 $15,176 $15,421 $24,232 10/31/2023 $13,879 $14,232 $23,723 11/30/2023 $15,333 $15,528 $25,889 12/31/2023 $16,916 $17,387 $27,066 1/31/2024 $16,999 $16,830 $27,520 2/29/2024 $18,591 $18,197 $28,990 3/31/2024 $19,051 $18,705 $29,923 4/30/2024 $17,891 $17,265 $28,700 5/31/2024 $18,664 $18,190 $30,124 6/30/2024 $19,226 $18,159 $31,204 7/31/2024 $19,235 $19,646 $31,584 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Since Inception
6/30/15 Class R4 at NAV 8.91% 4.15% 7.47% Russell 2000 Growth Index 12.80% 7.64% 7.72% S&P 500 Index Footnote Reference 22.15% 15.00% 13.50% | | |
| Performance Inception Date | | | Jun. 30, 2015 |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000151973 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class R5 | | |
| Trading Symbol | LADTX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B246"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R5 $72 0.69% | | |
| Expenses Paid, Amount | $ 72 | | |
| Expense Ratio, Percent | 0.69% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 9.17%, reflecting performance at the net asset value (NAV) of Class R5 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B251"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class R5 Russell 2000 Growth Index S&P 500 Index 6/30/2015 $10,000 $10,000 $10,000 7/31/2015 $10,022 $10,041 $10,210 8/31/2015 $8,972 $9,280 $9,594 9/30/2015 $8,437 $8,694 $9,356 10/31/2015 $8,509 $9,187 $10,145 11/30/2015 $8,715 $9,524 $10,176 12/31/2015 $8,300 $9,069 $10,015 1/31/2016 $7,229 $8,087 $9,518 2/29/2016 $7,035 $8,030 $9,505 3/31/2016 $7,451 $8,645 $10,150 4/30/2016 $7,403 $8,731 $10,189 5/31/2016 $7,613 $8,966 $10,372 6/30/2016 $7,620 $8,925 $10,399 7/31/2016 $8,225 $9,508 $10,783 8/31/2016 $8,312 $9,609 $10,798 9/30/2016 $8,454 $9,748 $10,800 10/31/2016 $7,858 $9,142 $10,603 11/30/2016 $8,257 $9,960 $10,996 12/31/2016 $8,095 $10,096 $11,213 1/31/2017 $8,427 $10,260 $11,426 2/28/2017 $8,739 $10,511 $11,879 3/31/2017 $8,779 $10,636 $11,893 4/30/2017 $8,846 $10,832 $12,015 5/31/2017 $8,897 $10,733 $12,184 6/30/2017 $9,138 $11,103 $12,260 7/31/2017 $9,308 $11,197 $12,512 8/31/2017 $9,340 $11,184 $12,551 9/30/2017 $9,790 $11,793 $12,810 10/31/2017 $10,091 $11,976 $13,109 11/30/2017 $10,348 $12,320 $13,511 12/31/2017 $10,545 $12,334 $13,661 1/31/2018 $10,952 $12,815 $14,443 2/28/2018 $11,059 $12,450 $13,911 3/31/2018 $11,304 $12,617 $13,557 4/30/2018 $11,557 $12,630 $13,609 5/31/2018 $12,751 $13,425 $13,937 6/30/2018 $13,008 $13,530 $14,023 7/31/2018 $12,948 $13,763 $14,544 8/31/2018 $14,632 $14,619 $15,018 9/30/2018 $14,597 $14,277 $15,104 10/31/2018 $12,557 $12,471 $14,072 11/30/2018 $12,422 $12,666 $14,358 12/31/2018 $11,106 $11,186 $13,062 1/31/2019 $12,866 $12,478 $14,109 2/28/2019 $14,267 $13,283 $14,562 3/31/2019 $14,116 $13,104 $14,845 4/30/2019 $14,464 $13,503 $15,446 5/31/2019 $14,086 $12,501 $14,464 6/30/2019 $15,411 $13,464 $15,483 7/31/2019 $15,865 $13,595 $15,706 8/31/2019 $15,028 $13,009 $15,457 9/30/2019 $13,672 $12,902 $15,746 10/31/2019 $13,970 $13,269 $16,087 11/30/2019 $14,472 $14,050 $16,671 12/31/2019 $14,695 $14,372 $17,175 1/31/2020 $15,013 $14,214 $17,168 2/29/2020 $14,430 $13,187 $15,755 3/31/2020 $12,206 $10,669 $13,809 4/30/2020 $14,238 $12,258 $15,579 5/31/2020 $16,155 $13,416 $16,321 6/30/2020 $17,183 $13,932 $16,645 7/31/2020 $18,325 $14,411 $17,584 8/31/2020 $19,394 $15,256 $18,848 9/30/2020 $19,929 $14,929 $18,132 10/31/2020 $20,416 $15,043 $17,650 11/30/2020 $23,080 $17,695 $19,582 12/31/2020 $25,415 $19,349 $20,335 1/31/2021 $26,504 $20,282 $20,129 2/28/2021 $27,508 $20,952 $20,684 3/31/2021 $25,852 $20,292 $21,590 4/30/2021 $27,019 $20,735 $22,742 5/31/2021 $25,376 $20,143 $22,901 6/30/2021 $26,608 $21,087 $23,436 7/31/2021 $26,113 $20,319 $23,993 8/31/2021 $26,804 $20,689 $24,722 9/30/2021 $25,643 $19,895 $23,572 10/31/2021 $27,091 $20,827 $25,224 11/30/2021 $24,880 $19,810 $25,049 12/31/2021 $24,801 $19,898 $26,172 1/31/2022 $20,162 $17,231 $24,817 2/28/2022 $20,176 $17,306 $24,074 3/31/2022 $20,034 $17,385 $24,968 4/30/2022 $17,354 $15,252 $22,791 5/31/2022 $16,869 $14,964 $22,833 6/30/2022 $15,807 $14,038 $20,948 7/31/2022 $17,332 $15,609 $22,879 8/31/2022 $17,290 $15,463 $21,946 9/30/2022 $15,914 $14,072 $19,925 10/31/2022 $16,891 $15,407 $21,538 11/30/2022 $16,948 $15,658 $22,742 12/31/2022 $15,893 $14,653 $21,432 1/31/2023 $17,226 $16,111 $22,778 2/28/2023 $17,069 $15,936 $22,223 3/31/2023 $17,226 $15,543 $23,038 4/30/2023 $16,805 $15,362 $23,398 5/31/2023 $17,083 $15,365 $23,500 6/30/2023 $17,796 $16,639 $25,053 7/31/2023 $18,024 $17,417 $25,857 8/31/2023 $16,798 $16,510 $25,446 9/30/2023 $15,494 $15,421 $24,232 10/31/2023 $14,175 $14,232 $23,723 11/30/2023 $15,665 $15,528 $25,889 12/31/2023 $17,283 $17,387 $27,066 1/31/2024 $17,375 $16,830 $27,520 2/29/2024 $19,000 $18,197 $28,990 3/31/2024 $19,478 $18,705 $29,923 4/30/2024 $18,302 $17,265 $28,700 5/31/2024 $19,086 $18,190 $30,124 6/30/2024 $19,670 $18,159 $31,204 7/31/2024 $19,677 $19,646 $31,584 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Since Inception
6/30/15 Class R5 at NAV 9.17% 4.40% 7.74% Russell 2000 Growth Index 12.80% 7.64% 7.72% S&P 500 Index Footnote Reference 22.15% 15.00% 13.50% | | |
| Performance Inception Date | | | Jun. 30, 2015 |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
| C000151974 | | | |
| Shareholder Report [Line Items] | | | |
| Fund Name | Lord Abbett Developing Growth Fund Inc. | | |
| Class Name | Class R6 | | |
| Trading Symbol | LADVX | | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Lord Abbett Developing Growth Fund Inc. for the period of August 1, 2023 to July 31, 2024, as well as certain changes to the Fund. | | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | | |
| Additional Information [Text Block] | You can find additional information about the Fund at lordabbett.com/FundDocuments | | |
| Additional Information Phone Number | 888-522-2388 | | |
| Additional Information Website | lordabbett.com/FundDocuments</span>" id="sjs-B272"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 20px; margin: 0px; overflow: visible; text-align: left;">lordabbett.com/FundDocuments</span> | | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R6 $62 0.59% | | |
| Expenses Paid, Amount | $ 62 | | |
| Expense Ratio, Percent | 0.59% | | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year and what affected its performance? For the fiscal year ended July 31, 2024, the Fund returned 9.30%, reflecting performance at the net asset value (NAV) of Class R6 shares, compared to the 12.80% of a securities market index with investment characteristics similar to those of the Fund, the Russell 2000 Growth Index. The Fund's broad-based market index, the S&P 500 Index, returned 22.15% over the same period. Positive factors for the markets included momentum around the soft-landing narrative, specifically in the second half of the period, which was supported by signs of a cooling labor market and a slowing economy, leading the market to adjust its expectations of future interest rate cuts by the U.S. Federal Reserve (the Fed). Negative factors, specifically in the beginning of the period, included stronger-than-expected GDP growth, resilient labor market data, and persistently high inflation readings that led to a more prolonged interest rate environment. Against this backdrop, U.S. equity markets delivered strong returns. Top contributors to performance: Top detractors from performance: | | |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is no guarantee of future results.</span>" id="sjs-B277"><span style="font-weight: 700; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">The Fund's past performance is no guarantee of future results.</span> | | |
| Line Graph [Table Text Block] | Class R6 Russell 2000 Growth Index S&P 500 Index 6/30/2015 $10,000 $10,000 $10,000 7/31/2015 $10,026 $10,041 $10,210 8/31/2015 $8,972 $9,280 $9,594 9/30/2015 $8,440 $8,694 $9,356 10/31/2015 $8,513 $9,187 $10,145 11/30/2015 $8,719 $9,524 $10,176 12/31/2015 $8,308 $9,069 $10,015 1/31/2016 $7,237 $8,087 $9,518 2/29/2016 $7,047 $8,030 $9,505 3/31/2016 $7,458 $8,645 $10,150 4/30/2016 $7,415 $8,731 $10,189 5/31/2016 $7,624 $8,966 $10,372 6/30/2016 $7,632 $8,925 $10,399 7/31/2016 $8,241 $9,508 $10,783 8/31/2016 $8,328 $9,609 $10,798 9/30/2016 $8,470 $9,748 $10,800 10/31/2016 $7,873 $9,142 $10,603 11/30/2016 $8,272 $9,960 $10,996 12/31/2016 $8,114 $10,096 $11,213 1/31/2017 $8,446 $10,260 $11,426 2/28/2017 $8,762 $10,511 $11,879 3/31/2017 $8,802 $10,636 $11,893 4/30/2017 $8,869 $10,832 $12,015 5/31/2017 $8,924 $10,733 $12,184 6/30/2017 $9,166 $11,103 $12,260 7/31/2017 $9,336 $11,197 $12,512 8/31/2017 $9,371 $11,184 $12,551 9/30/2017 $9,822 $11,793 $12,810 10/31/2017 $10,122 $11,976 $13,109 11/30/2017 $10,383 $12,320 $13,511 12/31/2017 $10,581 $12,334 $13,661 1/31/2018 $10,992 $12,815 $14,443 2/28/2018 $11,098 $12,450 $13,911 3/31/2018 $11,347 $12,617 $13,557 4/30/2018 $11,600 $12,630 $13,609 5/31/2018 $12,798 $13,425 $13,937 6/30/2018 $13,055 $13,530 $14,023 7/31/2018 $12,995 $13,763 $14,544 8/31/2018 $14,691 $14,619 $15,018 9/30/2018 $14,655 $14,277 $15,104 10/31/2018 $12,608 $12,471 $14,072 11/30/2018 $12,473 $12,666 $14,358 12/31/2018 $11,154 $11,186 $13,062 1/31/2019 $12,921 $12,478 $14,109 2/28/2019 $14,331 $13,283 $14,562 3/31/2019 $14,180 $13,104 $14,845 4/30/2019 $14,532 $13,503 $15,446 5/31/2019 $14,150 $12,501 $14,464 6/30/2019 $15,484 $13,464 $15,483 7/31/2019 $15,942 $13,595 $15,706 8/31/2019 $15,101 $13,009 $15,457 9/30/2019 $13,737 $12,902 $15,746 10/31/2019 $14,039 $13,269 $16,087 11/30/2019 $14,551 $14,050 $16,671 12/31/2019 $14,767 $14,372 $17,175 1/31/2020 $15,097 $14,214 $17,168 2/29/2020 $14,509 $13,187 $15,755 3/31/2020 $12,279 $10,669 $13,809 4/30/2020 $14,318 $12,258 $15,579 5/31/2020 $16,242 $13,416 $16,321 6/30/2020 $17,279 $13,932 $16,645 7/31/2020 $18,430 $14,411 $17,584 8/31/2020 $19,504 $15,256 $18,848 9/30/2020 $20,043 $14,929 $18,132 10/31/2020 $20,529 $15,043 $17,650 11/30/2020 $23,217 $17,695 $19,582 12/31/2020 $25,564 $19,349 $20,335 1/31/2021 $26,663 $20,282 $20,129 2/28/2021 $27,670 $20,952 $20,684 3/31/2021 $26,006 $20,292 $21,590 4/30/2021 $27,183 $20,735 $22,742 5/31/2021 $25,531 $20,143 $22,901 6/30/2021 $26,780 $21,087 $23,436 7/31/2021 $26,285 $20,319 $23,993 8/31/2021 $26,981 $20,689 $24,722 9/30/2021 $25,817 $19,895 $23,572 10/31/2021 $27,274 $20,827 $25,224 11/30/2021 $25,050 $19,810 $25,049 12/31/2021 $24,972 $19,898 $26,172 1/31/2022 $20,301 $17,231 $24,817 2/28/2022 $20,315 $17,306 $24,074 3/31/2022 $20,180 $17,385 $24,968 4/30/2022 $17,483 $15,252 $22,791 5/31/2022 $16,993 $14,964 $22,833 6/30/2022 $15,929 $14,038 $20,948 7/31/2022 $17,462 $15,609 $22,879 8/31/2022 $17,419 $15,463 $21,946 9/30/2022 $16,035 $14,072 $19,925 10/31/2022 $17,029 $15,407 $21,538 11/30/2022 $17,086 $15,658 $22,742 12/31/2022 $16,021 $14,653 $21,432 1/31/2023 $17,362 $16,111 $22,778 2/28/2023 $17,206 $15,936 $22,223 3/31/2023 $17,362 $15,543 $23,038 4/30/2023 $16,944 $15,362 $23,398 5/31/2023 $17,220 $15,365 $23,500 6/30/2023 $17,945 $16,639 $25,053 7/31/2023 $18,172 $17,417 $25,857 8/31/2023 $16,937 $16,510 $25,446 9/30/2023 $15,630 $15,421 $24,232 10/31/2023 $14,296 $14,232 $23,723 11/30/2023 $15,801 $15,528 $25,889 12/31/2023 $17,433 $17,387 $27,066 1/31/2024 $17,533 $16,830 $27,520 2/29/2024 $19,173 $18,197 $28,990 3/31/2024 $19,655 $18,705 $29,923 4/30/2024 $18,470 $17,265 $28,700 5/31/2024 $19,265 $18,190 $30,124 6/30/2024 $19,854 $18,159 $31,204 7/31/2024 $19,861 $19,646 $31,584 | | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Since Inception
6/30/15 Class R6 at NAV 9.30% 4.49% 7.85% Russell 2000 Growth Index 12.80% 7.64% 7.72% S&P 500 Index Footnote Reference 22.15% 15.00% 13.50% | | |
| Performance Inception Date | | | Jun. 30, 2015 |
| No Deduction of Taxes [Text Block] | The returns do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. | | |
| AssetsNet | $ 2,440,039,652 | $ 2,440,039,652 | $ 2,440,039,652 |
| Holdings Count | Holding | 89 | 89 | 89 |
| Advisory Fees Paid, Amount | $ 12,294,681 | | |
| InvestmentCompanyPortfolioTurnover | 122% | | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024 Total Net Assets $2,440,039,652 # of Portfolio Holdings 89 Portfolio Turnover Rate 122% Total Advisory Fees Paid $12,294,681 | | |
| Holdings [Text Block] | Portfolio Holdings Presented by Sector Footnote Reference % Footnote Reference Communication Services 1.44 % Consumer Discretionary 10.60 % Consumer Staples 6.41 % Financials 6.71 % Health Care 25.04 % Industrials 18.96 % Information Technology 27.87 % Repurchase Agreements 1.37 % Money Market Funds Footnote Reference 1.44 % Time Deposits Footnote Reference 0.16 % 100.00% Footnote Description Footnote A sector may comprise several industries Footnote Represents percent of total investments, which excludes derivatives. Footnote Securities were purchased with the cash collateral from loaned securities. | | |
| Material Fund Change [Text Block] | Summary of Fund Changes There were no material fund changes during the period. | | |
