Subsequent Events (Details) (USD $)	0 Months Ended
	Aug. 13, 2012 Issuance of Debt [Member]	Aug. 13, 2012 Minimum [Member] Issuance of Debt [Member]	Aug. 13, 2012 Maximum [Member] Issuance of Debt [Member]	Aug. 13, 2012 Line of Credit [Member] Refinancing of Debt [Member]	Jul. 31, 2012 Point Two Five Percent Convertible Senior Notes Due 2013 [Member]	Aug. 13, 2012 Point Two Five Percent Convertible Senior Notes Due 2013 [Member] Issuance of Debt [Member]	Jul. 31, 2012 4.0% Convertible Senior Notes due March 15, 2015 [Member]	Aug. 13, 2012 4.0% Convertible Senior Notes due March 15, 2015 [Member] Issuance of Debt [Member]	Aug. 13, 2012 LIBOR [Member] Line of Credit [Member] Minimum [Member] Issuance of Debt [Member]	Aug. 13, 2012 LIBOR [Member] Line of Credit [Member] Maximum [Member] Issuance of Debt [Member]	Aug. 13, 2012 Base Rate [Member] Line of Credit [Member] Minimum [Member] Issuance of Debt [Member]	Aug. 13, 2012 Base Rate [Member] Line of Credit [Member] Maximum [Member] Issuance of Debt [Member]	Aug. 13, 2012 Letter of Credit [Member] Deutsche Bank AG New York Branch, Bank of America, N.A., and Morgan Stanley Senior Funding, Inc. and Wells Fargo Bank [Member] Issuance of Debt [Member]	Aug. 13, 2012 Canadian Borrower [Member] Letter of Credit [Member] Deutsche Bank AG New York Branch, Bank of America, N.A., and Morgan Stanley Senior Funding, Inc. and Wells Fargo Bank [Member] Issuance of Debt [Member]
Subsequent Event [Line Items]
Credit facility, current borrowing capacity													$ 150,000,000
Credit facility, maximum borrowing capacity													200,000,000
Credit facility, borrowing capacity for Canadian dollar denominated loans to Canandian subsidiary														20,000,000
Credit facility margin on variable interest rate									2.00%	2.50%	1.00%	1.50%
Credit facility, unused capacity, commitment fee percentage		0.50%	0.375%
Interest rate on convertible notes					0.25%	0.25%	4.00%	4.00%
Letters of credit outstanding				41,000,000
Fixed-charge coverage ratio required per credit agreement	1
Credit facility, percent of excess availability for coverage ratio to apply			12.50%
Credit facility, amount of excess availability for coverage ratio to apply			15,000,000
Credit facility, minimum required unrestricted cash and cash equivalents		$ 200,000,000
Credit facility, covenant term, length of duration to stay, satisfy, bond or discharge material judgement	30 days