Share-Based Compensation (Details 1) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation [Line Items]
Total shares authorized	2,100,000
Shares available for future grants of stock options or restricted stock	1,700,000
Compensation Expense	$ 8,338	$ 8,146	$ 7,369
Income Tax Benefit	$ 2,210	$ 2,160	2,910
Stock Options [Roll Forward]
Outstanding at the beginning of the period (in shares)	263,888
Exercised (in shares)	(25,164)
Forfeited (in shares)	(1,666)
Outstanding at the end of the period (in shares)	237,058	263,888
Vested and Exercisable at the end of the period (in shares)	237,058
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 45.27
Exercised (in dollars per share)	43.74
Forfeited (in dollars per share)	47.72
Outstanding at the end of the period (in dollars per share)	45.44	$ 45.27
Vested and Exercisable at the end of period (in dollars per share)	$ 45.44
Weighted Average Remaining Contractual Term
Outstanding at the end of the period (in years)	2 years
Vested and Exercisable at the end of period (in years)	2 years
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 11,787
Vested and Exercisable at the end of the period	11,787
Stock options activity
Intrinsic Value of Stock Options Exercised	1,106	$ 1,634	5,991
Cash Received from Stock Options Exercised	1,473	1,791	7,502
Share-based Payment Arrangement, Exercise of Option, Tax Benefit	$ 727	$ 240	$ 2,003
Stock Options
Share-based Compensation [Line Items]
Expiration period	10 years
Restricted Stock
Restricted Stock
Unrecognized compensation cost related to unvested restricted stock	$ 11,000
Weighted average period during which unrecognized compensation cost is expected to be recognized (in years)	1 year 9 months 21 days
Number of Shares
Unvested at the beginning of the period (in shares)	314,487	320,103	270,523
Granted (in shares)	130,093	120,173	124,460
Vested (in shares)	(107,759)	(110,231)	(52,822)
Forfeited (in shares)	(26,872)	(15,558)	(22,058)
Unvested at the end of the period (in shares)	309,949	314,487	320,103
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 78.17	$ 69.36	$ 60.58
Granted (in dollars per share)	82.82	83.87	84.53
Vested (in dollars per share)	66.46	59.41	60.06
Forfeited (in dollars per share)	83.34	73.82	69.46
Unvested at the end of the period (in dollars per share)	$ 83.75	$ 78.17	$ 69.36
Grant Date Fair Value of Restricted Stock that Vested During the Year
Vested (in dollars)	$ 8,910	$ 9,081	$ 4,493
Service-Based Restricted Stock
Number of Shares
Unvested at the end of the period (in shares)	43,310
Restricted Stock Units (RSUs)
Share-based Compensation [Line Items]
Compensation Expense	$ 1,000	$ 600	$ 3,400
Number of Shares
Unvested at the beginning of the period (in shares)	52,064	116,489	154,832
Vested (in shares)	(52,064)	(62,252)	(29,281)
Forfeited (in shares)		(2,173)	(9,062)
Unvested at the end of the period (in shares)	0	52,064	116,489
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 63.92	$ 60.22	$ 59.04
Vested (in dollars per share)	82.23	57.00	58.74
Forfeited (in dollars per share)		63.92	60.17
Unvested at the end of the period (in dollars per share)	$ 0	$ 63.92	$ 60.22
Grant Date Fair Value of Restricted Stock that Vested During the Year
Vested (in dollars)	$ 4,311	$ 5,127	$ 2,516
Maximum [Member] | Restricted Stock
Share-based Compensation [Line Items]
Vesting period (in years)	4 years
Maximum [Member] | Restricted Stock Units (RSUs)
Share-based Compensation [Line Items]
Vesting period (in years)	4 years
Minimum [Member] | Restricted Stock
Share-based Compensation [Line Items]
Vesting period (in years)	1 year
Minimum [Member] | Restricted Stock Units (RSUs)
Share-based Compensation [Line Items]
Vesting period (in years)	3 years