Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amortized cost
Total	$ 1,022,078	$ 1,053,122
Gross unrealized holding gains
Total	15,257	30,279
Gross unrealized holding losses
Total	(20,568)	(4,327)
Fair value
Total Fair value	1,016,767	1,079,074
Debt issued by the U.S. government and agencies
Amortized cost
Due in one year or less	32	40
Fair value
Due in one year or less	32	40
Debt issued by government sponsored enterprises
Amortized cost
Due in one year or less		1,999
Due in one year - five years	227,945	140,352
Due in five years - ten years	94,777	95,602
Gross unrealized holding gains
Due in one year or less		5
Due in one year - five years	166	183
Due in five years - ten years	72	460
Gross unrealized holding losses
Due in one year - five years	(4,041)	(22)
Due in five years - ten years	(2,862)	(265)
Fair value
Due in one year or less		2,004
Due in one year - five years	224,070	140,513
Due in five years - ten years	91,987	95,797
Equity securities
Amortized cost
Total	5,298	13,301
Gross unrealized holding gains
Total	4,622	6,025
Gross unrealized holding losses
Total	(70)	(22)
Fair value
Total Fair value	9,850	19,304
Municipal securities
Amortized cost
Due in one year or less	710
Due in one year - five years	8,443	9,629
Due in five years - ten years	11,228	17,355
Due after ten years	71,068	100,644
Gross unrealized holding gains
Due in one year or less	10
Due in one year - five years	119	233
Due in five years - ten years	275	668
Due after ten years	1,111	5,679
Gross unrealized holding losses
Due after ten years	(386)
Fair value
Due in one year or less	720
Due in one year - five years	8,562	9,862
Due in five years - ten years	11,503	18,023
Due after ten years	71,793	106,323
Corporate debt issues
Amortized cost
Due after ten years	21,150	24,911
Gross unrealized holding gains
Due after ten years	475	483
Gross unrealized holding losses
Due after ten years	(449)	(2,691)
Fair value
Due after ten years	21,176	22,703
Residential mortgage-backed securities
Amortized cost
Total	581,427	649,289
Gross unrealized holding gains
Total	8,407	16,543
Gross unrealized holding losses
Total	(12,760)	(1,327)
Fair value
Total Fair value	577,074	664,505
Fixed rate | Pass-through
Amortized cost
Total	85,306	85,134
Gross unrealized holding gains
Total	3,041	6,266
Gross unrealized holding losses
Total	(1,075)
Fair value
Total Fair value	87,272	91,400
Fixed rate | Non-agency CMOs
Amortized cost
Total	3,894	5,700
Gross unrealized holding gains
Total	107	156
Gross unrealized holding losses
Total	(3)	(236)
Fair value
Total Fair value	3,998	5,620
Fixed rate | Agency CMOs
Amortized cost
Total	265,769	227,608
Gross unrealized holding gains
Total	1,060	3,462
Gross unrealized holding losses
Total	(11,436)	(744)
Fair value
Total Fair value	255,393	230,326
Variable rate | Pass-through
Amortized cost
Total	78,890	104,591
Gross unrealized holding gains
Total	3,525	5,314
Gross unrealized holding losses
Total	(16)	(6)
Fair value
Total Fair value	82,399	109,899
Variable rate | Non-agency CMOs
Amortized cost
Total	660	873
Gross unrealized holding losses
Total	(9)	(20)
Fair value
Total Fair value	651	853
Variable rate | Agency CMOs
Amortized cost
Total	146,908	225,383
Gross unrealized holding gains
Total	674	1,345
Gross unrealized holding losses
Total	(221)	(321)
Fair value
Total Fair value	$ 147,361	$ 226,407