Marketable Securities (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012
Marketable securities
Less than 12 months - Fair value	$ 452,468,000	$ 238,873,000
Less than 12 months - Unrealized loss	(15,690,000)	(1,401,000)
12 months or more - Fair value	175,906,000	37,237,000
12 months or more - Unrealized loss	(4,938,000)	(2,940,000)
Total - Fair value	628,374,000	276,110,000
Total - Unrealized loss	(20,628,000)	(4,341,000)
Number of investments that are temporarily impaired	119
Aggregate carrying amount of cost-method investment	1,138,000,000
U.S. government and agencies
Marketable securities
Less than 12 months - Fair value	213,915,000	70,128,000
Less than 12 months - Unrealized loss	(4,797,000)	(286,000)
12 months or more - Fair value	64,635,000	6,537,000
12 months or more - Unrealized loss	(2,106,000)	(1,000)
Total - Fair value	278,550,000	76,665,000
Total - Unrealized loss	(6,903,000)	(287,000)
Municipal securities
Marketable securities
Less than 12 months - Fair value	12,666,000
Less than 12 months - Unrealized loss	(413,000)
Total - Fair value	12,666,000
Total - Unrealized loss	(413,000)
Number of third party pricing sources	2
Maximum fair value as percentage of carrying value to compare the stated interest rate to current market rate	80.00%
Municipal securities for which book value exceeds carrying value	0
Corporate debt issues
Marketable securities
Less than 12 months - Fair value		850,000
Less than 12 months - Unrealized loss		(39,000)
12 months or more - Fair value	1,970,000	12,095,000
12 months or more - Unrealized loss	(449,000)	(2,652,000)
Total - Fair value	1,970,000	12,945,000
Total - Unrealized loss	(449,000)	(2,691,000)
Equity securities
Marketable securities
Less than 12 months - Fair value	552,000	601,000
Less than 12 months - Unrealized loss	(70,000)	(21,000)
12 months or more - Fair value		17,000
12 months or more - Unrealized loss		(1,000)
Total - Fair value	552,000	618,000
Total - Unrealized loss	(70,000)	(22,000)
Residential mortgage-backed securities | Non-agency CMOs
Marketable securities
Less than 12 months - Fair value	1,210,000
Less than 12 months - Unrealized loss	(12,000)
12 months or more - Fair value		4,357,000
12 months or more - Unrealized loss		(256,000)
Total - Fair value	1,210,000	4,357,000
Total - Unrealized loss	(12,000)	(256,000)
Residential mortgage-backed securities | Agency CMOs
Marketable securities
Less than 12 months - Fair value	224,125,000	167,294,000
Less than 12 months - Unrealized loss	(10,398,000)	(1,055,000)
12 months or more - Fair value	109,301,000	14,231,000
12 months or more - Unrealized loss	(2,383,000)	(30,000)
Total - Fair value	333,426,000	181,525,000
Total - Unrealized loss	$ (12,781,000)	$ (1,085,000)