Stockholders Equity Accumulated other comprehensive income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016		Dec. 31, 2016		Dec. 31, 2015
Accumulated other comprehensive income		$ 165,598	$ 185,918		$ 149,555		$ 114,532
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax		15,494	73,274
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax		549	(1,888)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated other comprehensive income		172,165	190,999		156,963	[1]	120,787	[1]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax	[1]	14,834	71,283
Accumulated Other-than-Temporary Impairment [Member]
Accumulated other comprehensive income		971	925		311		(114)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax		660	1,991
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated other comprehensive income		(7,538)	(6,006)		$ (7,719)		$ (6,141)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments, Net of Tax		0	0
reclassifications out of accumulated other comprehensive income [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax		549	(1,888)
reclassifications out of accumulated other comprehensive income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	[1]	368	(1,071)	[2]
reclassifications out of accumulated other comprehensive income [Member] | Accumulated Other-than-Temporary Impairment [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	[2]	0	(952)
reclassifications out of accumulated other comprehensive income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, Net of Tax		$ 181	$ 135

[1] Includes the impact of taxes, deferred acquisition costs, value of insurance in force acquired, unearned revenue reserves and policyholder liabilities. See Note 2 for further information.

[2] See Note 2 for further information.