Employee Benefit and Deferred Compensation Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in benefit obligation
Benefit obligation at beginning of year	$ 27,364,000
Benefit obligation at end of year	28,087,000	27,364,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	27,989,000
Contribution by employer	0	0
Fair value of plan assets at end of year	26,532,000	27,989,000
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	27,364,000	19,428,000
Service cost	0	0	0
Interest cost	1,292,000	899,000	863,000
Plan participants’ contributions	0	0
Actuarial loss (gain)	2,601,000	(1,344,000)
Benefits paid	(3,170,000)	(1,372,000)
Addition from business combination	0	9,753,000
Benefit obligation at end of year	28,087,000	27,364,000	19,428,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	27,989,000	16,008,000
Actual return on plan assets	1,713,000	3,776,000
Contribution by employer	0	0
Benefits paid	(3,170,000)	(1,372,000)
Addition from business combination	0	9,577,000
Fair value of plan assets at end of year	26,532,000	27,989,000	16,008,000
Funded status at end of year	(1,555,000)	625,000
Weighted-average assumptions as of December 31
Discount rate (percent)	4.00%	4.83%
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	2,082,000	1,543,000
Service cost	14,000	28,000	23,000
Interest cost	84,000	70,000	65,000
Plan participants’ contributions	77,000	95,000
Actuarial loss (gain)	(118,000)	505,000
Benefits paid	(198,000)	(159,000)
Addition from business combination	0	0
Benefit obligation at end of year	1,941,000	2,082,000	1,543,000
Change in fair value of plan assets
Benefits paid	(198,000)	(159,000)
Funded status at end of year	$ (1,941,000)	$ (2,082,000)
Weighted-average assumptions as of December 31
Discount rate (percent)	3.22%	4.66%