8. Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	$ 417,766	$ 382,138
Other comprehensive income, net of tax	35,628	163,193	$ (121,772)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	1,300	33,700	71,200
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(32,400)	(37,500)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Tax	0	0
Other comprehensive income, net of tax	(32,400)	(37,500)
Other Postretirement Benefit Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	(18,600)	(20,700)	(16,300)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	500	(6,800)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,500	1,100
Other Comprehensive Income (Loss), Tax	(900)	1,300
Other comprehensive income, net of tax	2,100	(4,400)
Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	435,000	369,100	164,000
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	105,100	325,400
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(800)	(900)
Other Comprehensive Income (Loss), Tax	(38,400)	(119,400)
Other comprehensive income, net of tax	65,900	205,100
Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	417,700	382,100	$ 218,900
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	73,200	281,100
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,700	200
Other Comprehensive Income (Loss), Tax	(39,300)	(118,100)
Other comprehensive income, net of tax	$ 35,600	$ 163,200