Dividends From Subsidiaries And Statutory Financial Information (Schedule of Combined Net Income and Policyholders' Surplus in Accordance with Statutory Accounting Practices) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Amount available for dividend distribution without prior approval from regulatory authorities	$ 699,000
Net income	698,862	$ 702,830	$ 813,303
Policyholders' surplus	5,479,603	$ 5,493,044	$ 5,296,435
Increase in BIC's statutory capital and surplus	$ 277,000
Total Adjusted Capital percentage threshold	200.00%
BIC's Total Adjusted Capital balance	$ 5,200,000
BIC's Total Adjusted Capital balance as percentage of RBC Authorized Control Level	397.00%