Dividends and Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
	May 14, 2020	Jun. 27, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Dividends [Abstract]
Cash dividends declared per share of common stock (in dollars per share)			$ 7.25	$ 7.05	$ 7.25	$ 7.05
Basic Earnings per Common Share [Abstract]
Common stock equivalent shares (in shares)			0	0	0	0
Net Income			$ 14,309	$ 14,105	$ 28,431	$ 27,654
Weighted Average Number of Common Shares Outstanding (in shares)			793,556	787,307	793,530	785,881
Basic and Diluted Earnings Per Common Share (in dollars per share)			$ 18.03	$ 17.92	$ 35.83	$ 35.19
Mid-Year Cash Dividend Declared in 2020 [Member]
Dividends [Abstract]
Dividends payable, date declared					May 14, 2020
Cash dividends declared per share of common stock (in dollars per share)	$ 7.25
Percentage increase in cash dividend per share	2.80%
Dividends payable, date paid					Jul. 01, 2020
Dividends payable, date of record					Jun. 12, 2020
Mid-Year Cash Dividend Declared in 2019 [Member]
Dividends [Abstract]
Cash dividends paid per share of common stock (in dollars per share)		$ 7.05
Dividends payable, date paid					Jun. 27, 2019