Shareholders' Equity, Stock Repurchase Program, Dividends and Issuance of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Stock Repurchased [Abstract]
Total consideration for shares to be purchased	$ 31,200		$ 31,152
Per share price of shares purchased (in dollars per share)	$ 700
Minimum [Member]
Stock Issued [Abstract]
Per share price of shares issued (in dollars per share)		$ 715	$ 635
Maximum [Member]
Stock Issued [Abstract]
Per share price of shares issued (in dollars per share)		$ 770	$ 690
Directors and Officers [Member]
Stock Issued [Abstract]
Issuance of common stock (in shares)			2,400
Non-qualified Deferred Compensation Retirement Plans [Member]
Stock Issued [Abstract]
Issuance of common stock (in shares)		9,312	13,520
Common Stock Repurchase Plan [Member]
Stock Repurchased [Abstract]
Approved funds available for common stock repurchase program		$ 20,000
Number of shares of stock purchased (in shares)		0	0