Long-Term Debt (Details) (USD $) In Thousands, unless otherwise specified				1 Months Ended	6 Months Ended			6 Months Ended
	Dec. 31, 2012	Jun. 30, 2012	Oct. 21, 2011 Swing line loan [Member]	Apr. 30, 2012 Senior unsecured revolving credit facility [Member]	Dec. 31, 2012 Senior unsecured revolving credit facility [Member]	Apr. 13, 2012 Senior unsecured revolving credit facility [Member]	Oct. 21, 2011 Senior unsecured revolving credit facility [Member]	Dec. 31, 2012 Senior unsecured revolving credit facility [Member] Minimum [Member]	Dec. 31, 2012 Senior unsecured revolving credit facility [Member] Maximum [Member]
Line of Credit Facility [Line Items]
Current borrowing capacity						$ 387,500	$ 250,000
Maximum borrowing capacity			25,000
Additional borrowings				137,500
Increase to borrowing capacity in future periods						150,000
Long-term debt	$ 230,500	$ 229,000
Description of variable rate basis					LIBOR
Basis spread on LIBOR								1.25%	1.50%
Weighted average interest rate					1.63%
Commitment fee (percentage)								0.175%	0.225%
Interest coverage ratio					3.5
Senior leverage ratio					2.75
Ratio of earnings before interest, taxes, depreciation and amortization to interest expense					3.0