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
	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance		$ 25,960
Reclassified from other comprehensive income	2,723
Reported in earnings	(3,245)
Ending Balance	0	25,960
Securities Redeemed at Less Than Par Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cash received for redemptions	$ (25,438)