Share-based payments (Details) (USD $)	3 Months Ended			12 Months Ended																		12 Months Ended											12 Months Ended	1 Months Ended	12 Months Ended
	Feb. 03, 2012	Jan. 28, 2011	Apr. 30, 2010	Feb. 03, 2012	Jan. 28, 2011	Jan. 29, 2010	Feb. 03, 2012 Management-owned shares, Rollover Options, and vested time and performance options Y Day	Feb. 03, 2012 Stock options Y	Jan. 28, 2011 Stock options Y	Jan. 29, 2010 Stock options Y	Feb. 03, 2012 Equity Appreciation Rights	Jan. 28, 2011 Equity Appreciation Rights	Jan. 29, 2010 Equity Appreciation Rights	Feb. 03, 2012 Restricted stock unit awards	Jan. 28, 2011 Restricted stock unit awards	Jan. 29, 2010 Restricted stock unit awards	Feb. 03, 2012 Restricted shares	Jan. 28, 2011 Restricted shares	Jan. 29, 2010 Restricted shares	Feb. 03, 2012 Prior equity award plan exchange Stock options Rollover Options Y	Feb. 03, 2012 2007 Stock incentive plan	Feb. 03, 2012 2007 Stock incentive plan Stock options Time Options Y	Jan. 28, 2011 2007 Stock incentive plan Stock options Time Options	Jan. 29, 2010 2007 Stock incentive plan Stock options Time Options	Feb. 03, 2012 2007 Stock incentive plan Stock options Time Options Maximum	Feb. 03, 2012 2007 Stock incentive plan Stock options Time Options Minimum	Feb. 03, 2012 2007 Stock incentive plan Stock options Performance Options Y	Jan. 28, 2011 2007 Stock incentive plan Stock options Performance Options	Jan. 29, 2010 2007 Stock incentive plan Stock options Performance Options	Feb. 03, 2012 2007 Stock incentive plan Stock options Performance Options Maximum	Feb. 03, 2012 2007 Stock incentive plan Stock options Performance Options Minimum	Feb. 03, 2012 2007 Stock incentive plan Stock options Non-qualified stock options	Feb. 03, 2012 2007 Stock incentive plan Restricted stock unit awards Non-employee directors	Nov. 27, 2009 2007 Stock incentive plan Restricted shares	Feb. 03, 2012 Rights plan
Share-based payments
Number of shares of common stock authorized for grant																					31,142,858
Shares available for future grants																					19,338,127
Vesting period (in years)																									5 years	4 years				5 years	4 years		3 years
Weighted average for key assumptions used in determining the fair value
Expected dividend yield (as a percent)								0.00%	0.00%	0.00%
Expected stock price volatility (as a percent)								38.70%	39.10%	41.20%
Weighted average risk-free interest rate (as a percent)								2.30%	2.80%	2.80%
Expected term of options (in years)								6.8	7.0	7.4
Contractual term of options (in years)								P10Y
Expiration period of call option subsequent to the date of grant (in years)																						5					5
Put right period after termination due to the death or disability of the holder of the instrument (in days)							365
Period after the date of grant within which the put option can occur (in years)							5
Options Issued
Balance at the beginning of the period (in shares)																						5,778,131					5,497,024					211,755
Granted (in shares)																						91,012					91,012
Exercised (in shares)																						(1,427,179)					(1,437,711)
Canceled (in shares)																						(183,383)					(182,088)
Balance, at the end of the period (in shares)																						4,258,581	5,778,131				3,968,237	5,497,024				211,755
Vested or expected to vest at the end of the period (in shares)																						4,159,595					3,853,900
Exercisable at the end of the period (in shares)																				5,382		2,486,048					3,098,603
Average Exercise Price
Balance at the beginning of the period (in dollars per share)																						$ 9.73					$ 9.82
Granted (in dollars per share)																						$ 29.98					$ 29.98
Exercised (in dollars per share)																						$ 8.41					$ 8.36
Canceled (in dollars per share)																						$ 11.09					$ 11.13
Balance at the end of the period (in dollars per share)																						$ 10.55	$ 9.73				$ 10.75	$ 9.82
Vested or expected to vest at the end of the period (in dollars per share)																						$ 10.36					$ 10.53
Exercisable at the end of the period (in dollars per share)																				$ 2.1875		$ 9.08					$ 9.42
Remaining Contractual Term (in years)
Balance, at the end of the period (in years)																						6.3					6.4
Vested or expected to vest at the end of the period (in years)																						6.3					6.4
Exercisable at the end of the period (in years)																				2.2		6.1					6.1
Intrinsic Value
Balance at the end of the period																						$ 133,691,000					$ 123,780,000
Vested or expected to vest at the end of the period																						131,357,000					121,044,000
Exercisable at the end of the period																				200,000		81,692,000					100,756,000
Weighted average grant date fair value (in dollars per share)																						$ 13.47	$ 12.61	$ 6.73			$ 13.47	$ 12.61	$ 6.73
Total unrecognized compensation cost								16,900,000																									200,000
Expected weighted average expense recognition period (in years)								2.5
Equity appreciation rights, nonvested restricted stock and restricted stock unit awards
Granted (in shares or rights)																																			818,847
Vested (in shares or rights)																																			768,561
Vested with stock offerings (in shares or rights)																																		508,572
Canceled (in shares or rights)																																			50,286
Outstanding at the end of the period (in shares or rights)																																	13,024
Restricted shares or units - additional disclosures
Total fair value																																		11,500,000
Awards granted, purchase price (in dollars per unit)														$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Share-based compensation expense
Pre-tax	8,600,000	3,800,000	13,300,000	23,981,000	30,171,000	22,245,000		15,121,000	12,722,000	11,686,000	8,731,000	17,366,000	7,237,000	129,000	83,000	840,000			2,482,000
Net of tax	$ 5,300,000	$ 2,300,000	$ 8,100,000	$ 14,604,000	$ 18,393,000	$ 13,587,000		$ 9,208,000	$ 7,755,000	$ 7,138,000	$ 5,317,000	$ 10,587,000	$ 4,420,000	$ 79,000	$ 51,000	$ 513,000			$ 1,516,000