EARNINGS PER SHARE (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share Reconciliation [Abstract]
Basic weighted-average shares outstanding									46,372	45,823	45,237
Incremental Common Shares Attributable To Employee Share Based Payment Arrangements									567	426	389
Incremental Common Shares Attributable To Deferred Director Share Based Compensation Arrangements									74	73	69
Diluted weighted-average shares outstanding									47,013	46,322	45,695
Net earnings	$ 39,751	$ 34,360	$ 31,796	$ 24,516	$ 36,581	$ 27,784	$ 25,898	$ 16,335	$ 130,423	$ 106,598	$ 95,221
Basic earnings per share	$ 0.85	$ 0.74	$ 0.69	$ 0.53	$ 0.80	$ 0.61	$ 0.57	$ 0.36	$ 2.81	$ 2.33	$ 2.10
Diluted earnings per share	$ 0.84	$ 0.73	$ 0.68	$ 0.52	$ 0.79	$ 0.60	$ 0.56	$ 0.35	$ 2.77	$ 2.30	$ 2.08