Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation Of Unrecognized Tax Benefits [Line Items]
Balance at beginning of year	$ 46,845	$ 39,425	$ 33,322
Additions based on tax positions related to the current year	5,702	6,035	4,243
Additions for tax positions of prior years	2,172	7,966	3,493
Reductions for tax positions for prior years	(5,025)	(481)	(624)
Reduction for lapse in statute of limitations	(2,658)	(4,563)	(451)
Settlements	(1,581)	(1,537)	(558)
Balance at end of year	$ 45,455	$ 46,845	$ 39,425