Basis of Financial Reporting Text Block (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 12,107,000
Insurance Commissions	$ 333,583,000	$ 671,578,000
Profit-Sharing Contingent Commission Revenue	(13,981,000)	(25,665,000)
Fees and Commissions, Other	113,388,000	237,251,000
Operating Leases, Future Minimum Payments Due	191,800,000	191,800,000			210,400,000
Share-based Compensation		15,027,000	$ 15,326,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance Commissions		14,800,000
Profit-Sharing Contingent Commission Revenue		17,000,000.0
Fees and Commissions, Other		(2,400,000)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 117,500,000	$ 117,515,000
Cost to Obtain [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Costs	$ 6,600,000	6,600,000
Capitalized Contract Cost, Amortization		100,000
Cost to Fulfill [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Costs				$ 52,700,000
Capitalized Contract Cost, Amortization		$ 3,900,000