Policy Claims and Benefits (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense	$ 6,584,668	$ 5,896,469
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(432,582)	(455,547)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,152,086	5,440,922
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Current Year Claims and Claims Adjustment Expense	5,457,193	5,046,146
Prior Year Claims and Claims Adjustment Expense	58,249	66,022
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	5,515,442	5,112,168
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(1,063,092)	(1,097,105)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(3,978,853)	(3,518,791)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(5,041,945)	(4,615,896)
Liability for Unpaid Claims and Claims Adjustment Expense, Interest Accretion	13,185	12,299
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	2,663	(117,352)
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	15,848	(105,053)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,641,431	5,832,141
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	524,808	439,568
Liability for Claims and Claims Adjustment Expense	$ 7,166,239	$ 6,271,709