CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 186,515	$ 188,323	$ 176,668
Net Changes in Fair Value of Cash Flow Hedges:
Net of Income Tax (Expense) Benefit of $(44), $(121), and $(305)	133	364	485
Supplemental Executive Retirement Plan Adjustments:
Net of Income Tax (Expense) Benefit of $1,059, $(747), and $637	(3,190)	2,026	(2,156)
Total Other Comprehensive Income (Loss), Net of Tax	(3,057)	2,390	(1,671)
Total Comprehensive Income	$ 183,458	$ 190,713	$ 174,997