CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Condensed Consolidating Statements of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net earnings	$ 19,516	$ 6,054	$ 28,354	$ 8,232
Unrealized (loss) gain on short-term investments	(42)	17	(23)	67
Changes in pension plan assets and benefit obligations	(2)	(8)	(6)	(12)
Total comprehensive income net of income taxes	19,472	6,063	28,325	8,287
Parent Company Only (issuer) [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings	19,769	6,054	28,607	8,232
Unrealized (loss) gain on short-term investments	(42)	17	(23)	67
Changes in pension plan assets and benefit obligations	(2)	(8)	(6)	(12)
Total comprehensive income net of income taxes	19,472	6,063	28,325	8,287
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings	4,269	5,156	8,608	6,912
Unrealized (loss) gain on short-term investments
Changes in pension plan assets and benefit obligations
Total comprehensive income net of income taxes	4,522	5,156	8,861	6,912
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings	(4,522)	(5,156)	(8,861)	(6,912)
Unrealized (loss) gain on short-term investments
Changes in pension plan assets and benefit obligations
Total comprehensive income net of income taxes	$ (4,522)	$ (5,156)	$ (8,861)	$ (6,912)