Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share of Common Stock Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Basic And Diluted [Line Items]
Net income			$ 136,917	$ 280,278
Weighted average shares outstanding	69,109	71,622	68,932	71,395
Total weighted average shares outstanding	69,892	72,604	69,676	72,263
Diluted [Member]
Earnings Per Share Basic And Diluted [Line Items]
Net income	34,873	172,656	136,917	280,278
Weighted average shares outstanding	69,109	71,622	68,932	71,395
Employee stock options	783	982	744	868
Total weighted average shares outstanding	69,892	72,604	69,676	72,263
Earnings per share	0.50	2.38	$ 1.97	$ 3.88
Basic [Member]
Earnings Per Share Basic And Diluted [Line Items]
Net income	34,873	172,656	$ 136,917	$ 280,278
Weighted average shares outstanding	69,109	71,622	68,932	71,395
Employee stock options	0	0	0	0
Total weighted average shares outstanding	69,109	71,622	68,932	71,395
Earnings per share	0.50	2.41	$ 1.99	$ 3.93