Investments and Marketable Securities - Aggregate Market Value and Unrealized Losses of Investments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	15	56
Aggregate Market Value, Unrealized Loss Less 12 months	$ 11,417	$ 45,577
Unrealized Losses, Unrealized Loss Less 12 months	(10)	(53)
Number of investments, Unrealized Loss Greater 12 months	69	16
Aggregate Market Value, Unrealized Loss Greater 12 months	84,505	10,144
Unrealized Losses, Unrealized Loss Greater 12 months	(713)	(446)
Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	0	4
Aggregate Market Value, Unrealized Loss Less 12 months	0	5,179
Unrealized Losses, Unrealized Loss Less 12 months	0	(3)
Number of investments, Unrealized Loss Greater 12 months	3	1
Aggregate Market Value, Unrealized Loss Greater 12 months	23,207	1,790
Unrealized Losses, Unrealized Loss Greater 12 months	(19)	0
State and Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	5	19
Aggregate Market Value, Unrealized Loss Less 12 months	7,368	24,969
Unrealized Losses, Unrealized Loss Less 12 months	(8)	(27)
Number of investments, Unrealized Loss Greater 12 months	4	1
Aggregate Market Value, Unrealized Loss Greater 12 months	6,559	1,092
Unrealized Losses, Unrealized Loss Greater 12 months	(20)	(1)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	9	33
Aggregate Market Value, Unrealized Loss Less 12 months	3,031	15,429
Unrealized Losses, Unrealized Loss Less 12 months	(2)	(23)
Number of investments, Unrealized Loss Greater 12 months	60	14
Aggregate Market Value, Unrealized Loss Greater 12 months	51,757	7,262
Unrealized Losses, Unrealized Loss Greater 12 months	(673)	(445)
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investments, Unrealized Loss Less 12 months	1
Aggregate Market Value, Unrealized Loss Less 12 months	1,018
Unrealized Losses, Unrealized Loss Less 12 months	0
Number of investments, Unrealized Loss Greater 12 months	2
Aggregate Market Value, Unrealized Loss Greater 12 months	2,982
Unrealized Losses, Unrealized Loss Greater 12 months	$ (1)