Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 151,461	$ 21,186	$ 382,724	$ 201,150
Other comprehensive income (loss), net of tax:
Unrealized (losses) gains on securities	(14,662)	13,929	(73,933)	52,014
Foreign currency translation adjustment	3,001	11,415	(11,296)	23,558
Pension benefit adjustment	118	85,891	357	93,061
Total other comprehensive income (loss), net of tax	(11,543)	111,235	(84,872)	168,633
Comprehensive income	139,918	132,421	297,852	369,783
Less: Comprehensive loss attributable to noncontrolling interests	(19)	(192)	(142)	(760)
Comprehensive income attributable to the Company	$ 139,937	$ 132,613	$ 297,994	$ 370,543

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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