Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			$ 732,573
Total amount reclassified from Accumulated other comprehensive loss, net of tax	$ 0	$ 0	720	$ 15,359
Unrealized gain on available-for-sale securities (Note 16)	124	27	62	563
Other comprehensive income (loss)	7,883	1,020	(11,304)	19,299
Balance at end of period	748,654		748,654
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(121,746)	(117,266)	(124,848)	(115,517)
Tax benefit	(1,079)	(1,384)	(2,146)	(2,050)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	3,090	1,378	6,192	3,401
Balance at end of period	(118,656)	(115,888)	(118,656)	(115,888)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent | Adjustments for New Accounting Pronouncement
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at end of period	0	(3,772)	0	(3,772)
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0	0	0
Tax benefit	0	0	0	0
Total amount reclassified from Accumulated other comprehensive loss, net of tax	0	0	0	0
Balance at end of period	0	0	0	0
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest | Adjustments for New Accounting Pronouncement
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at end of period	0	0	0	0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	(52)	11	(104)	(94)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	0	0	0	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	4,221	2,751	8,442	5,545
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	0	0	0	0
Accumulated Net Investment Gain (Loss) Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(56)	(36)
Unrealized gain on available-for-sale securities (Note 16)	124	27	62	563
Other comprehensive income (loss)			6	(572)
Balance at end of period	68	(9)	68	(9)
Accumulated Net Investment Gain (Loss) Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0
Unrealized gain on available-for-sale securities (Note 16)	0	0	0	0
Other comprehensive income (loss)			0	0
Balance at end of period	0	0	0	0
Accumulated Foreign Currency Adjustment Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(111,273)	(87,261)	(18,181)	(30)
Total amount reclassified from Accumulated other comprehensive loss, net of tax			(720)	(15,359)
Other comprehensive income (loss)	4,651	(248)	(89,161)	(102,838)
Balance at end of period	(106,622)	(87,509)	(106,622)	(87,509)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	308	639	(97)	6
Total amount reclassified from Accumulated other comprehensive loss, net of tax			0	0
Other comprehensive income (loss)	18	(137)	423	496
Balance at end of period	$ 326	$ 502	$ 326	$ 502