Investments (Realized and unrealized gains) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Net realized gains on investments	$ 2,724	$ 2,244	$ 2,140	$ 6,413
Change in net unrealized gains (losses) on investments	31,428	(34,676)	78,872	(1,449)
Total net realized and change in net unrealized gains (losses) on investments	34,152	(32,432)	81,012	4,964
Managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	3,306	6,140	6,523	12,449
Gross realized losses	(786)	(4,036)	(5,089)	(6,165)
Net realized gains on investments	2,520	2,104	1,434	6,284
Change in net unrealized gains (losses) on investments	30,052	(33,926)	77,130	743
Total net realized and change in net unrealized gains (losses) on investments	32,572	(31,822)	78,564	7,027
Non-managed investments
Fixed Maturities Short Term And Other Investments And Cash Equivalents [Abstract]
Gross realized gains	204	140	715	140
Gross realized losses	0	0	(9)	(11)
Net realized gains on investments	204	140	706	129
Change in net unrealized gains (losses) on investments	1,376	(750)	1,742	(2,192)
Total net realized and change in net unrealized gains (losses) on investments	$ 1,580	$ (610)	$ 2,448	$ (2,063)