Equity (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 165,346
Ending Balance	78,932
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(234)	$ (402)
Change in OCI before reclassifications	(923)	23
Amounts reclassified from AOCI	0	0
Income tax benefit (expense)	194	(8)
Ending Balance	(1,013)	(387)
Net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	165,580	71,377
Change in OCI before reclassifications	(145,519)	23,059
Amounts reclassified from AOCI	490	4,144
Income tax benefit (expense)	30,501	(9,521)
Ending Balance	79,962	89,059
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	0	0
Change in OCI before reclassifications	(22)	0
Amounts reclassified from AOCI	0	0
Income tax benefit (expense)	5	0
Ending Balance	(17)	0
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	165,346	70,975
Change in OCI before reclassifications	(146,464)	23,082
Amounts reclassified from AOCI	490	4,144
Income tax benefit (expense)	30,700	(9,529)
Ending Balance	78,932	88,672
Cash flow hedges | Net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(18,000)	41,000
Ending Balance	(41,000)	$ 31,000
ASU 2016-01 | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	0
ASU 2016-01 | Net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	(1,539)
ASU 2016-01 | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	0
ASU 2016-01 | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	(1,539)
ASU 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	30,400
ASU 2018-02 | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	(50)
ASU 2018-02 | Net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	30,449
ASU 2018-02 | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	0
ASU 2018-02 | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of adoption	$ 30,399