Earnings Per Common Share Basic and Diluted (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator-basic and diluted
Net income	$ 23,486	$ 7,747	$ 47,166	$ 26,178
Denominator
Weighted average number of common shares outstanding-basic	39,143	40,592	39,272	40,475
Effect of dilutive stock options	589	646	592	804
Effect of dilutive convertible notes		229		737
Effect of dilutive restricted shares	561	607	592	656
Weighted average number of common shares outstanding - diluted	40,293	42,074	40,456	42,672
Earnings per common share-basic	$ 0.60	$ 0.19	$ 1.20	$ 0.65
Earnings per common share-diluted	$ 0.58	$ 0.18	$ 1.17	$ 0.61
Antidilutive stock options and restricted shares	3,593	3,530	3,541	2,806