Summary of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	$ 17,239		$ 22,594
Gross Unrealized Gains	11,789		9,875
Gross Unrealized Losses	(3)		(41)
Fair Value	29,025		32,428
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	17,235		22,590
Gross Unrealized Gains	11,781		9,868
Gross Unrealized Losses	(3)		(41)
Fair Value	29,013		32,417
Debt Securities | Corporate Debt Obligations
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	15,451		20,747
Gross Unrealized Gains	124		158
Gross Unrealized Losses	(3)		(39)
Fair Value	15,572		20,866
Debt Securities | Mortgage and Asset Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	68		101
Gross Unrealized Gains	10		10
Gross Unrealized Losses	0		0
Fair Value	78		111
Debt Securities | Private Debt Obligations
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	1,716	[1]	1,742	[1]
Gross Unrealized Gains	11,647	[1]	9,700	[1]
Gross Unrealized Losses	0	[1]	(2)	[1]
Fair Value	13,363	[1]	11,440	[1]
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost / Amortized Cost	4		4
Gross Unrealized Gains	8		7
Gross Unrealized Losses	0		0
Fair Value	$ 12		$ 11

[1] Through December 31, 2009, certain private debt obligations experienced other-than-temporary losses and $13.2 million of impairments were recorded. Unrealized gains of private debt obligations are stated as the difference between their fair value and cost basis, net of impairment.