Debt (Details) (USD $)	0 Months Ended		1 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended
	Jun. 15, 2011	Apr. 21, 2011	Apr. 04, 2008	Mar. 31, 2012	Apr. 04, 2008 Term Loans [Member]	Mar. 31, 2012 Term Loans [Member]	Dec. 31, 2011 Term Loans [Member]	Apr. 02, 2011 Term Loans [Member]	Jan. 01, 2011 Term Loans [Member]	Apr. 04, 2008 Revolving Loans [Member]	Apr. 21, 2011 Senior Notes [Member]
Debt Instrument [Line Items]
Credit facility					$ 150,000,000
Revolving loans borrowing amount			200,000,000							100,000,000
Possible additional credit facility			100,000,000
Ending date of repayment				April 4, 2013
Repayment on outstanding Credit Facility						3,750,000	3,750,000	3,750,000	3,750,000
Credit facility outstanding at end of period						90,000,000		105,000,000
Senior notes, principal amount		175,000,000
Issuance of Senior Notes, principal amount	75,000,000	100,000,000
Senior Notes, principal outstanding				$ 175,000,000
Debt instrument interest rate											5.20%
Debt instrument maturity date											June 15, 2018