Debts and Letters of Credit (Details) (USD $) In Millions, except Per Share data, unless otherwise specified			1 Months Ended	3 Months Ended		3 Months Ended					3 Months Ended			1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2012 letter	Jul. 02, 2011	Jan. 31, 2012 Revolving Credit Facility Y	Mar. 31, 2012 Revolving Credit Facility Y	Jan. 20, 2012 Revolving Credit Facility	Mar. 31, 2012 Revolving Credit Facility Alternate base rate	Mar. 31, 2012 Revolving Credit Facility Adjusted LIBOR rate	Mar. 31, 2012 Maximum Revolving Credit Facility	Mar. 31, 2012 Maximum Revolving Credit Facility Alternate base rate	Mar. 31, 2012 Maximum Revolving Credit Facility Adjusted LIBOR rate	Mar. 31, 2012 Minimum Revolving Credit Facility	Mar. 31, 2012 Minimum Revolving Credit Facility Alternate base rate	Mar. 31, 2012 Minimum Revolving Credit Facility Adjusted LIBOR rate	Jun. 30, 2006 1% senior convertible notes	Mar. 31, 2012 1% senior convertible notes Y	Apr. 02, 2011 1% senior convertible notes	Mar. 31, 2012 1% senior convertible notes Y	Apr. 02, 2011 1% senior convertible notes	Jul. 02, 2011 1% senior convertible notes	Oct. 03, 2009 1% senior convertible notes	Jun. 05, 2006 1% senior convertible notes
Details of long-term debt
Total long-term debt	$ 300.8	$ 285.8													$ 300.8		$ 300.8		$ 285.8	$ 266.5
Interest rate on Senior convertible notes (as a percent)															1.00%		1.00%				1.00%
Aggregate principal amount of convertible debt																					425.0
Proceeds from issuance of convertible notes after issuance costs														415.9
Conversion price of convertible debt (in dollars per share)															$ 30.30		$ 30.30
Percentage of principal amount that the holder of the note may require the entity to repurchase the debt instrument on May 15, 2013, 2016, and 2021																	100.00%
Percentage of principal amount that the holder of the note may require the entity to repurchase due to certain fundamental changes undergone by the entity																	100.00%
Percentage of principal amount at which the entity may redeem some or all of the notes on or after May 20, 2013																	100.00%
Discount rate used to calculate the carrying value of the liability component of the convertible debt (as a percent)																					8.10%
Variable rate basis on which discount rate is based						Base rate	LIBOR							7-year swap
Carrying value of the equity component of convertible debt																				158.5
Remaining term of convertible notes (in years)															1.1		1.1
Deferred finance costs				1.9																	9.1
Liability component, debt issuance cost														5.7
Equity component, debt issuance cost														3.4
Unamortized portion of debt issuance cost				1.8											0.9		0.9
Fair market value of convertible debt															326.2		326.2		332.1
Carrying amounts of the liability and equity components:
Carrying amount of equity component, net of equity issuance cost															158.5		158.5		158.5
Principal amount of 1% Senior Coupon Notes															325.0		325.0		325.0
Unamortized discount of liability component															(24.2)		(24.2)		(39.2)
Effective interest rate and interest expense for the contractual interest and the amortization of debt discount:
Effective interest rate (as a percent)															8.10%	8.10%	8.10%	8.10%
Interest expense-contractual interest															0.8	0.8	2.4	2.4
Interest expense-amortization of debt discount															5.1	4.7	15.0	13.9
Variable interest rate base						Base rate	LIBOR							7-year swap
Credit facility term (in years)			5
Maximum borrowing capacity under the credit agreement					250.0
Maximum borrowing capacity optional expansion				100
Percentage points added to the reference rate									2.00%	3.00%		0.75%	1.75%
Commitment fee on the unused portion of the credit facility (as a percent)								0.50%			0.25%
Minimum cash and permitted investments agreed to be maintained under the terms of revolving credit facility				200
Period of amortization of interest expenses capitalized (in years)				5
Outstanding balance				0
Outstanding Letters of Credit
Number of standby letters of credit	16
Letters of credit outstanding	$ 36.5