Policy Claims and Benefits Policy Claims and Benefits (Rollforward of Claims and Claim Adjustment Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense Beginning Balance	$ 5,896,469	$ 5,180,802	$ 4,977,836
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Beginning Balance	(455,547)	(394,821)	(405,583)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Beginning Balance	5,440,922	4,785,981	4,572,253
Current Year Claims and Claims Adjustment Expense	10,048,866	8,911,640	8,562,036
Prior Year Claims and Claims Adjustment Expense	131,181	14,364	(134,765)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	10,180,047	8,926,004	8,427,271
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(4,602,535)	(4,513,606)	(4,385,839)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(4,691,722)	(4,004,038)	(3,777,137)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(9,294,257)	(8,517,644)	(8,162,976)
Interest On Liability For Policy And Contract Claims	24,802	19,443	18,151
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(199,428)	227,138	(68,718)
Liability for Unpaid Claims and Claims Adjustment Expense Other	(174,626)	246,581	(50,567)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Ending Balance	6,152,086	5,440,922	4,785,981
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Ending Balance	432,582	455,547	394,821
Liability for Claims and Claims Adjustment Expense, Ending Balance	$ 6,584,668	$ 5,896,469	$ 5,180,802