Basis and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Franchise Royalties and Fees		$ 12,862	$ 14,201
Operating Expenses		390,232	328,825
OPERATING PROFIT		70,064	86,489
EARNINGS BEFORE INCOME TAXES		66,752	82,623
INCOME TAXES		14,506	29,323
NET EARNINGS		52,246	53,300
Deferred Income Taxes Payable		241,137		$ 222,592
Customer Deposits and Advance Payments		74,150		68,060
Total Liabilities		962,817		964,260
Retained Earnings		1,867,895		1,819,524
Total Shareholders’ Equity		1,756,192		1,728,004
Total Liabilities & Shareholders’ Equity		2,719,009		$ 2,692,264
Comprehensive Income		51,769	$ 53,503
ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, amortization period	5 years
Balance Without ASC 606 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Franchise Royalties and Fees		10,766
Operating Expenses		388,396
OPERATING PROFIT		69,804
EARNINGS BEFORE INCOME TAXES		66,492
INCOME TAXES		14,442
NET EARNINGS		52,050
Deferred Income Taxes Payable		241,696
Customer Deposits and Advance Payments		72,058
Total Liabilities		961,284
Retained Earnings		1,869,428
Total Shareholders’ Equity		1,757,725
Total Liabilities & Shareholders’ Equity		2,719,009
Comprehensive Income		51,573
Effect of Change Higher/(Lower) | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue	$ 2,400
Franchise Royalties and Fees		2,096
Operating Expenses		1,836
OPERATING PROFIT		260
EARNINGS BEFORE INCOME TAXES		260
INCOME TAXES		64
NET EARNINGS		196
Deferred Income Taxes Payable		(559)
Customer Deposits and Advance Payments		2,092
Total Liabilities		1,533
Retained Earnings	$ 2,400	(1,533)
Total Shareholders’ Equity		(1,533)
Total Liabilities & Shareholders’ Equity		0
Comprehensive Income		$ 196