Reinsurance (Narrative) (Details) - USD ($) $ in Thousands									3 Months Ended		9 Months Ended		21 Months Ended	36 Months Ended		48 Months Ended
	Jul. 01, 2019	Jan. 01, 2018	Jan. 01, 2017	Dec. 31, 2013	Jul. 01, 2012	Dec. 31, 2010	Dec. 31, 2009	Jan. 31, 2001	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2013	Dec. 31, 2017	Dec. 31, 2013	Dec. 31, 2018
Effects of Reinsurance [Line Items]
Ceded Premiums									$ (466,593)	$ (437,696)	$ (1,379,545)	$ (1,306,564)
Reinsurance recoverables									42,921,981		42,921,981							$ 34,682,127
PAR U
Effects of Reinsurance [Line Items]
Reinsurance recoverables									12,277,299		12,277,299							11,444,032
PURC
Effects of Reinsurance [Line Items]
Reinsurance recoverables									4,510,249		4,510,249							4,127,455
PARCC
Effects of Reinsurance [Line Items]
Reinsurance recoverables									2,666,372		2,666,372							2,527,690
GUL Re
Effects of Reinsurance [Line Items]
Reinsurance recoverables									2,211,909		2,211,909							2,017,810
PAR Term
Effects of Reinsurance [Line Items]
Reinsurance recoverables									1,827,497		1,827,497							1,678,745
Prudential of Taiwan
Effects of Reinsurance [Line Items]
Reinsurance recoverables									1,439,389		1,439,389							1,414,669
Term Re
Effects of Reinsurance [Line Items]
Reinsurance recoverables									1,456,210		1,456,210							1,259,141
Prudential Insurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables									1,975,165		1,975,165							1,226,917
DART
Effects of Reinsurance [Line Items]
Reinsurance recoverables									275,156		275,156							$ 119,946
Union Hamilton Reinsurance, Ltd.
Effects of Reinsurance [Line Items]
Reinsurance recoverables									$ 3,100,000		$ 3,100,000
Union Hamilton Reinsurance, Ltd. | Quote Share Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage													50.00%
Affiliated Entity | PAR U
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage					95.00%	70.00%
Affiliated Entity | PURC
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage														95.00%	70.00%
Affiliated Entity | PARCC
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage	100.00%						90.00%
Ceded Premiums	$ (476,000)
Ceded Expenses and Reserves	$ (409,000)
Affiliated Entity | GUL Re
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage			95.00%	30.00%
Affiliated Entity | PAR Term
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage	100.00%																95.00%
Ceded Premiums	$ (150,000)
Ceded Expenses and Reserves	$ (115,000)
Affiliated Entity | Prudential of Taiwan
Effects of Reinsurance [Line Items]
Related Party Transaction, Term								2 years
Affiliated Entity | Term Re
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage																95.00%
Affiliated Entity | Prudential Insurance
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage											100.00%
Affiliated Entity | DART
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage		95.00%