Investments (Realized and unrealized gains) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Net realized gains on investments	$ 4,397	$ (1,187)	$ 6,537	$ 5,226
Change in net unrealized gains on investments	5,459	3,916	84,331	2,467
Total net realized and change in net unrealized gains (losses) on investments	9,856	2,729	90,868	7,693
Managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	4,544	1,826	11,067	14,275
Gross realized losses	(464)	(3,059)	(5,553)	(9,224)
Net realized gains on investments	4,080	(1,233)	5,514	5,051
Change in net unrealized gains on investments	4,652	1,765	81,782	2,508
Total net realized and change in net unrealized gains (losses) on investments	8,732	532	87,296	7,559
Non-managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	317	46	1,032	186
Gross realized losses	0	0	(9)	(11)
Net realized gains on investments	317	46	1,023	175
Change in net unrealized gains on investments	807	2,151	2,549	(41)
Total net realized and change in net unrealized gains (losses) on investments	$ 1,124	$ 2,197	$ 3,572	$ 134