Fair Value Measurements - Reconciliation of Assets Measured at Fair Value on Recurring Basis using Unobservable Inputs Level 3 (Detail) (Auction Rate Securities [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 25,960
Reclassified from other comprehensive income	2,723
Reported in earnings	(3,245)
Ending Balance	0
Securities Redeemed at Less Than Par Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash received for redemptions	$ (25,438)