Other Comprehensive Income (Loss) and Related Tax Effects (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,299,244,000	$ 2,357,597,000	$ 2,027,867,000	$ 2,299,244,000	$ 1,755,023,000
Cumulative Effect on Retained Earnings, Net of Tax	18,208,000
Other Comprehensive Income (Loss), Net of Tax		(9,578,000)	8,505,000	(40,077,000)	15,677,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,317,452,000	2,378,144,000	2,049,032,000	2,378,144,000	2,049,032,000
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax				0	0
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(52,251,000)			(52,251,000)	(59,038,000)
Cumulative Effect on Retained Earnings, Net of Tax	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				(38,485,000)	13,956,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				0	0
Other Comprehensive Income (Loss), Net of Tax				(38,485,000)	13,956,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(52,251,000)	(90,736,000)	(45,082,000)	(90,736,000)	(45,082,000)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(571,000)			(571,000)	(1,681,000)
Cumulative Effect on Retained Earnings, Net of Tax	433,000
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				(199,000)	(1,577,000)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(4,000)	3,298,000
Other Comprehensive Income (Loss), Net of Tax				(203,000)	1,721,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(138,000)	(341,000)	40,000	(341,000)	40,000
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(52,822,000)	(82,089,000)	(53,547,000)	(52,822,000)	(60,719,000)
Cumulative Effect on Retained Earnings, Net of Tax	433,000
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				(38,684,000)	12,379,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(4,000)	3,298,000
Other Comprehensive Income (Loss), Net of Tax		(8,988,000)	8,505,000	(38,688,000)	15,677,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (52,389,000)	$ (91,077,000)	$ (45,042,000)	$ (91,077,000)	$ (45,042,000)