Restatement and Revision of Previously Issued Unaudited Financial Statements - Effect of Revisions on Affected Line Items on Condensed Consolidated Statement of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Condensed Consolidated Statement of Comprehensive Income Data:
Net income (loss)	$ (17,271)	$ 60,645	$ 78,325
Comprehensive income	(17,176)	60,808
As Previously Reported [Member]
Condensed Consolidated Statement of Comprehensive Income Data:
Net income (loss)	31,130	61,071
Comprehensive income	31,225	61,234
Revisions [Member]
Condensed Consolidated Statement of Comprehensive Income Data:
Net income (loss)		(426)
Comprehensive income		(426)
As Revised [Member]
Condensed Consolidated Statement of Comprehensive Income Data:
Net income (loss)		60,645
Comprehensive income		$ 60,808