Basis of presentation and accounting policies (Detail 4) (USD $)	12 Months Ended
Jan. 30, 2015	Jan. 31, 2014	Feb. 01, 2013
Impairment of long-lived assets
Minimum period for which stores are open to be reviewed for impairment	3 years
Impairment charges included in SG&A expense	$ 1,900,000	$ 500,000	$ 2,700,000
Goodwill and other intangible assets
Impairment of intangible assets	0	0	0
Accrued expenses and other
Compensation and benefits	78,645,000	47,909,000
Insurance	81,944,000us-gaap_SelfInsuranceReserveCurrent	84,697,000us-gaap_SelfInsuranceReserveCurrent
Taxes (other than taxes on income)	124,893,000	104,990,000
Other	128,278,000us-gaap_OtherAccruedLiabilitiesCurrent	130,982,000us-gaap_OtherAccruedLiabilitiesCurrent
Accrued expenses and other	413,760,000us-gaap_AccruedLiabilitiesCurrent	368,578,000us-gaap_AccruedLiabilitiesCurrent
Operating leases and related liabilities
Deferred rent liability	54,600,000us-gaap_DeferredRentCredit	49,500,000us-gaap_DeferredRentCredit
Contingent rent liability	4,800,000dg_ContingentRentLiabilityCurrent	6,000,000dg_ContingentRentLiabilityCurrent
Noncurrent other liabilities
Compensation and benefits	20,266,000	17,604,000
Insurance	140,916,000us-gaap_SelfInsuranceReserveNoncurrent	145,162,000us-gaap_SelfInsuranceReserveNoncurrent
Income tax related reserves	10,690,000	18,802,000
Deferred gain on sale leaseback	58,215,000	62,693,000
Other	55,222,000	52,285,000
Noncurrent other liabilities	$ 285,309,000us-gaap_OtherLiabilitiesNoncurrent	$ 296,546,000us-gaap_OtherLiabilitiesNoncurrent

Represents the minimum period for which stores are open to be reviewed for impairment.

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Represents the contingent rent liability derived from specified sales based targets at the balance sheet date.

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The noncurrent portion of the gain that will be recorded as income or a reduction in rent expense in future periods less amounts recognized in the current period.

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Carrying value as of the Balance Sheet date of obligations incurred and payable for sales, use, payroll, excise, real, property and other taxes, other than income taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Aggregate carrying value as of the balance sheet date of the liabilities for deferred compensation arrangements payable after one year (or the normal operating cycle, if longer). Represents currently earned compensation under cash arrangements (such as a profit-sharing plan, rabbi trust, and employee contract--excluding equity-based arrangements) that is not actually paid until a later date.

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The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Total loss recognized during the period from the impairment of goodwill plus the loss recognized in the period resulting from the impairment of the carrying amount of intangible assets, other than goodwill.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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The noncurrent portion of the amount recognized for uncertain tax positions as of the balance sheet date.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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The noncurrent portion (due beyond one year or one operating cycle) of other accrued expenses (expenses incurred at the end of the reporting period but not yet paid) not otherwise defined in the taxonomy.

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Aggregate carrying amount, as of the balance sheet date, of noncurrent obligations not separately disclosed in the balance sheet. Noncurrent liabilities are expected to be paid after one year (or the normal operating cycle, if longer).

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Carrying amount of accrued known and estimated losses incurred as of the balance sheet date for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property that are expected to be paid within one year (or the normal operating cycle, if longer).

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Carrying amount of accrued known and estimated losses incurred as of the balance sheet date for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property that are expected to be paid after one year (or the normal operating cycle, if longer).

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