Earnings Per Share - Reconciliation of Basic Average Common Shares Outstanding to Diluted Average Common Shares Outstanding (Detail) (USD $) In Thousands, except 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 [Abstract]
Net income	$ 44,767	$ 64,883	$ 186,475	$ 209,416
Basic average common shares outstanding	177,527,000	176,164,000	177,102,000	175,830,000
Effect of dilutive stock options	2,125,000	1,970,000	1,929,000	1,322,000
Diluted weighted average common shares outstanding	179,652,000	178,134,000	179,031,000	177,152,000
Earnings per share:
Basic	$ 0.25	$ 0.37	$ 1.05	$ 1.19
Diluted	$ 0.25	$ 0.36	$ 1.04	$ 1.18