Investments Fair Value and Gross Unrealized Losses of Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 6,984	$ 628	$ 1,993
Available-for-sale Securities, Gross Realized Losses	(4,376)	(346)	(280)
Available-for-sale Securities, Net Realized Gain (Loss)	2,608	282	1,713
Unrealized loss position, Less than 12 Months, fair value	26,086
Unrealized loss position, Less than 12 Month, Gross Unrealized Losses	(5,033)
Unrealized loss position, 12 Months or Greater, Fair Value	803
Unrealized loss position, 12 Month or Greater, Gross Unrealized Losses	(451)
Unrealized loss position, Total, Fair Value	26,889	20,641
Unrealized loss position, Total, Gross Unrealized Losses	(5,484)	(2,257)
Corporate obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position, Less than 12 Months, fair value	10,477
Unrealized loss position, Less than 12 Month, Gross Unrealized Losses	(276)
Unrealized loss position, 12 Months or Greater, Fair Value	0
Unrealized loss position, 12 Month or Greater, Gross Unrealized Losses	0
Unrealized loss position, Total, Fair Value	10,477	14,252
Unrealized loss position, Total, Gross Unrealized Losses	(276)	(277)
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position, Less than 12 Months, fair value	15,609
Unrealized loss position, Less than 12 Month, Gross Unrealized Losses	(4,757)
Unrealized loss position, 12 Months or Greater, Fair Value	803
Unrealized loss position, 12 Month or Greater, Gross Unrealized Losses	(451)
Unrealized loss position, Total, Fair Value	16,412	6,389
Unrealized loss position, Total, Gross Unrealized Losses	$ (5,208)	$ (1,980)