SOI Net investment income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net investment income
Investment income before expenses		$ 1,295,541	$ 1,273,008	$ 1,248,381
Investment expenses		(18,982)	(18,578)	(19,993)
Net investment income		1,276,559	1,254,430	1,228,388
Fixed maturity and short-term investments
Net investment income
Investment income before expenses		819,047	796,133	816,907
Mortgage loans on real estate
Net investment income
Investment income before expenses		142,478	150,284	149,497
Policy loans
Net investment income
Investment income before expenses		199,737	206,081	207,013
Limited partnership interests
Net investment income
Investment income before expenses		1,759	10,462	9,128
Net interest on funds withheld balances under reinsurance agreements, related party
Net investment income
Investment income before expenses		22,045	22,165	21,295
Derivative instruments (1)
Net investment income
Investment income before expenses	[1]	100,007	78,655	39,533
Other
Net investment income
Investment income before expenses		$ 10,468	$ 9,228	$ 5,008

[1] Includes gains (losses) on the hedged asset for fair value hedges.