Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 155,091	$ 121,895	$ 231,263	$ 179,964
Other comprehensive income (loss), net of tax:
Unrealized (losses) gains on securities	(12,475)	12,634	(59,271)	38,085
Foreign currency translation adjustment	(10,545)	8,709	(14,297)	12,143
Pension benefit adjustment	119	3,637	239	7,170
Total other comprehensive income (loss), net of tax	(22,901)	24,980	(73,329)	57,398
Comprehensive income	132,190	146,875	157,934	237,362
Less: Comprehensive loss attributable to noncontrolling interests	(49)	(362)	(123)	(568)
Comprehensive income attributable to the Company	$ 132,239	$ 147,237	$ 158,057	$ 237,930

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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