Future Policy Benefit Reserve (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Future policy benefit reserves are comprised of the following:
Traditional life	$ 756,470	$ 737,252
Annuities	2,854,456	2,768,795
Total future policy benefit reserves	3,610,926	3,506,047
Reinsurance recoverable from GCLR	3,191,584	3,072,615
Funds withheld on GreyCastle life retrocession arrangements (net of future policy benefit reserves recoverable	$ 999,219	$ 998,968
Other information:
Average interest rate used for future policy benefits, percent	4.00%	4.00%
GreyCastle Life Reinsurance SAC Ltd
Future policy benefit reserves are comprised of the following:
Reinsurance recoverable from GCLR	$ 3,191,584	$ 3,072,615
Assets held on a funds withheld basis relating to the GreyCastle Life Retro Arrangements	4,190,803	4,071,583
U.S. Term Life Reinsurance [Member]
Future policy benefit reserves are comprised of the following:
Reinsurance recoverable from GCLR	242,762	270,238
Other Life Retrocessions [Member]
Future policy benefit reserves are comprised of the following:
Reinsurance recoverable from GCLR	8,321	10,997
Corporate and other | GreyCastle Life Reinsurance SAC Ltd
Future policy benefit reserves are comprised of the following:
Net future policy benefit reserves	$ 168,259	$ 152,197