Fair Value Measurements and Derivative Instruments (Details 3) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 348,697,000	$ 325,368,000
Gross unrealized gains	5,109,000	3,504,000
Gross unrealized losses	(2,727,000)	(6,580,000)
Estimated fair value	351,079,000	322,292,000
Investment securities at a loss position for more than 12 months, aggregate unrealized holding losses	2,000,000	1,000,000
Investment securities at a loss position for more than 12 months, estimated fair value	48,000,000	19,000,000
Investment securities at a loss position for less than 12 months, aggregate unrealized holding losses	1,000,000	6,000,000
Investment securities at a loss position for less than 12 months, estimated fair value	85,000,000	182,000,000
Amortized cost - Within 1 year	41,708,000
Estimated fair value - Within 1 year	41,807,000
Amortized cost - After 1 year through 5 years	72,219,000
Estimated fair value - After 1 year through 5 years	72,921,000
Amortized cost - After 5 years through 10 years	78,486,000
Estimated fair value - After 5 years through 10 years	78,919,000
Amortized cost - After 10 years	156,284,000
Estimated fair value - After 10 years	157,432,000
Amortized cost - Total	348,697,000
Estimated fair value - Total	351,079,000
Debt securities - U.S. and foreign governments, agencies and municipalities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	133,573,000	121,803,000
Gross unrealized gains	1,813,000	999,000
Gross unrealized losses	(1,094,000)	(3,372,000)
Estimated fair value	134,292,000	119,430,000
Debt securities - corporate
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	64,761,000	37,901,000
Gross unrealized gains	1,354,000	935,000
Gross unrealized losses	(302,000)	(572,000)
Estimated fair value	65,813,000	38,264,000
Mortgage-backed / asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	150,363,000	165,664,000
Gross unrealized gains	1,942,000	1,570,000
Gross unrealized losses	(1,331,000)	(2,636,000)
Estimated fair value	$ 150,974,000	$ 164,598,000