Information Pertaining to Held to Maturity Bond with Gross Unrealized Losses (Detail) (Corporate Bonds, USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Corporate Bonds
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months Fair Value	$ 67,361
Less than 12 months Gross Unrealized Losses	(151)
12 months or longer Fair Value	2,549
12 months or longer Gross Unrealized Losses	(16)
Total Fair Value	69,910	72,315
Total Gross Unrealized Losses	$ (167)	$ (664)