Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 997,452	[1]	$ 210,981		$ 925,275
Other comprehensive income (loss) before reclassifications, net of tax	(777,022)		800,841		(716,918)
Reclassifications, net of tax	11,517		(14,370)		2,624
Other comprehensive income (loss)	(765,505)		786,471		(714,294)
Ending balance	231,947		997,452	[1]	210,981
Available for Sale Assets [Member]
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,090,273		256,196		1,024,367
Other comprehensive income (loss) before reclassifications, net of tax	(759,976)		855,132		(758,857)
Reclassifications, net of tax	2,036		(21,055)		(9,314)
Other comprehensive income (loss)	(757,940)		834,077		(768,171)
Ending balance	332,333		1,090,273		256,196
Deferred Acquisition Costs [Member]
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(10,758)		(6,728)		(16,417)
Other comprehensive income (loss) before reclassifications, net of tax	5,643		(4,030)		9,689
Reclassifications, net of tax	0		0		0
Other comprehensive income (loss)	5,643		(4,030)		9,689
Ending balance	(5,115)		(10,758)		(6,728)
Foreign Exchange [Member]
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	17,386		24,866		26,608
Other comprehensive income (loss) before reclassifications, net of tax	(13,759)		(7,480)		(1,742)
Reclassifications, net of tax	0		0		0
Other comprehensive income (loss)	(13,759)		(7,480)		(1,742)
Ending balance	3,627		17,386		24,866
Pension Adjustments [Member]
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(99,449)		(63,353)		(109,283)
Other comprehensive income (loss) before reclassifications, net of tax	(8,930)		(42,781)		33,992
Reclassifications, net of tax	9,481		6,685		11,938
Other comprehensive income (loss)	551		(36,096)		45,930
Ending balance	$ (98,898)		$ (99,449)		$ (63,353)

[1] Certain balances were adjusted to give effect to discontinued operations as described in Note 1—Significant Accounting Policies.