Accumulated Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Equity [Abstract]
Amounts reclassified from AOCI, sale of securities tax expense (benefit)	$ 8,221	$ 8,906
Amounts reclassified from AOCI, pension tax expense (benefit)	2,449	1,159
Unrealized holding gains (losses) arising during the period, tax expense (benefit)	(67,787)	65,575
Unrealized adjustment to deferred policy acquisition costs, tax expense (benefit)	11,232	6,525
Unrealized gains on investments attributable to participating policyholders' interest, tax expense (benefit)	2,528	2,984
Foreign currency adjustment, tax benefit	$ 1,124	$ 311