Deferred Compensation Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Text Details [Line Items]
Comprehensive pension gain (loss), net of tax	$ (1,387,000)	$ (606,000)	$ 1,365,000
Comprehensive pension gain (loss)	(1,387,000)	(606,000)	1,365,000
Amounts not recognized as net periodic benefit, net of tax	(6,326,000)	(7,713,000)
Pension loss adjustment, net of tax	900,000	600,000	(1,400,000)
FDBP [Member]
Deferred Compensation Text Details [Line Items]
Benefit payments	0
Estimated future employer contributions, next year	0
Benefit obligation	$ 400,000	0
Comprehensive pension gain (loss), net of tax		0
Discount rate	1.60%
Change in discount rate	0.15%
Comprehensive pension gain (loss)		0
Amounts not recognized as net periodic benefit, net of tax		0
FDBP [Member] | Maximum [Member]
Deferred Compensation Text Details [Line Items]
Comprehensive pension gain (loss), net of tax	$ (100,000)
Comprehensive pension gain (loss)	(100,000)
Amounts not recognized as net periodic benefit, net of tax	100,000
ESBP [Member]
Deferred Compensation Text Details [Line Items]
Estimated future employer contributions, next year	600,000
Benefit obligation	5,200,000	6,400,000
Comprehensive pension gain (loss), net of tax	$ (300,000)	$ (400,000)
Discount rate	3.76%	3.06%
Change in discount rate	0.70%
Increase (decrease) in plan liabilities	$ (1,200,000)
Comprehensive pension gain (loss)	(300,000)	$ (400,000)
Amounts not recognized as net periodic benefit, net of tax	900,000	1,400,000
NDBP [Member]
Deferred Compensation Text Details [Line Items]
Benefit obligation	$ 12,200,000	$ 13,400,000
Discount rate	1.90%	1.80%
Change in discount rate	0.10%
Increase (decrease) in plan liabilities	$ (1,200,000)
Targeted minimum return	4.00%	4.00%
Guaranteed return	4.00%	4.00%
Amounts not recognized as net periodic benefit, net of tax	$ 5,200,000	$ 6,100,000
BDBP [Member]
Deferred Compensation Text Details [Line Items]
Benefit obligation	$ 9,800,000	$ 9,700,000
Discount rate	1.75%	1.62%
Change in discount rate	0.13%
Increase (decrease) in plan liabilities	$ 100,000
Targeted minimum return	3.25%	3.25%
BDBP [Member]
Deferred Compensation Text Details [Line Items]
Amounts not recognized as net periodic benefit, net of tax	$ 700,000	$ 300,000
ESBP, NDBP, BDBP and FDBP [Member]
Deferred Compensation Text Details [Line Items]
Benefit obligation	27,597,000	29,498,000	28,460,000
Pension loss adjustment, net of tax	300,000	100,000	(1,800,000)
Amount to be recognized as components of net periodic benefit in next year	200,000
Employer contributions	1,181,000	1,152,000
Key Employee Non Qualified Deferred Compensation Plan [Member]
Deferred Compensation Text Details [Line Items]
Employer contributions	0	100,000	200,000
Non Employee Director Deferred Compensation Plan [Member]
Deferred Compensation Text Details [Line Items]
Employer contributions	$ 1,100,000	$ 500,000	$ 400,000