Employee Benefit Plans (Details Textual)	12 Months Ended
	Dec. 31, 2016 USD ($) quarter hour year	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
401(k) and Profit Sharing Plans
401(k) and Profit Sharing Plans
Minimum age required to be considered eligible for plan | year	21
Period of Employment Required to be Eligible for Plan	3 months
Minimum number of quarters required to be eligible for employer discretionary contribution | quarter	1
Minimum number of hours required to be considered eligible for employer discretionary contribution | hour	501
Percent rate for non-elective safe harbor contribution as component of profit sharing plan	3.00%
Profit Sharing Plan Expense	$ 9,041,000	$ 8,017,000	$ 7,107,000
Maximum percentage of annual compensation allowable for contribution by eligible employees	60.00%
Percentage of amount out of first specific percent of employee's contribution matched under plan	50.00%
Percentage of employee's contribution required to determine the matched amount under the plan	6.00%
Company's contribution to the plan	$ 2,946,000	2,629,000	2,246,000
Deferred Compensation Plans
401(k) and Profit Sharing Plans
Percentage of salary for deferral of cash payments	50.00%
Percentage of bonuses and directors fees for deferral of cash payments	100.00%
Total amount deferred	$ 967,000	720,000	591,000
Credit earning rate as a percentage of return on equity	50.00%
Total earnings for the plan	$ 431,000	386,000	369,000
Liability related to obligations of deferred compensation plans	11,273,000	11,971,000
Supplemental Employee Retirement Plan
401(k) and Profit Sharing Plans
Company's contribution to the plan	$ 299,000	224,000	151,000
Credit earning rate as a percentage of return on equity	50.00%
Total earnings for the plan	$ 85,000	$ 69,000	$ 59,000