Reinsurance (Reinsurance Recoverable by Counterparty) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	$ 32,555,500	$ 28,674,226
PAR U
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	11,111,272	10,514,125
PALAC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	8,388,988	7,706,860
PURC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	3,577,962	3,153,449
PARCC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	2,546,673	2,589,397
GUL Re
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	1,772,950	0
PAR Term
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	1,559,618	1,403,738
Prudential of Taiwan
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	1,406,686	1,246,241
Prudential Insurance
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	1,152,241	976,652
Term Re
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	966,509	593,084
UPARC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	0	467,904
Unaffiliated
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	$ 72,601	$ 22,776