Basis of Financial Reporting Text Block (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	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	$ 349,490,000
Profit-Sharing Contingent Commission Revenue	(11,684,000)
Fees and Commissions, Other	112,368,000
Operating Leases, Future Minimum Payments Due	199,600,000		210,400,000
Share-based Compensation	7,295,000	$ 8,564,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance Commissions	46,000,000.0
Profit-Sharing Contingent Commission Revenue	18,200,000
Fees and Commissions, Other	(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			$ 117,515,000
Cost to Obtain [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Costs	2,800,000
Capitalized Contract Cost, Amortization	31,700
Cost to Fulfill [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Costs	52,700,000
Capitalized Contract Cost, Amortization	$ 10,100,000