Investments (Reclassifications of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Cash flow hedges - Currency/Interest rate
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	$ 3,599	$ (523)	$ 2,772	$ 1,278
Net unrealized investments gains (losses) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	85,002	2,453	70,905	2,766
Total net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	88,601	1,930	73,677	4,044
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	$ 88,601	$ 1,930	$ 73,677	$ 4,044