Capital and Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	$ 429,289	$ 429,519	$ 476,419	$ 522,411	$ 503,394	$ 492,508	$ 476,419	$ 492,508
Other comprehensive income (loss)	1,379			(2,330)			(184)	(2,731)
Balance at end of year	469,590	429,289	429,519	517,683	522,411	503,394	469,590	517,683
Unrealized loss on available-for-sale debt securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	(274)	(274)	(274)	(274)	(274)	(274)	(274)	(274)
Other comprehensive income (loss)	0	0	0	0	0	0
Deconsolidation of API (see Note 3)			0
Balance at end of year	(274)	(274)	(274)	(274)	(274)	(274)	(274)	(274)
Unrealized (loss) gain on derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	0	0	(14)	(184)	241	(277)	(14)	(277)
Other comprehensive income (loss)	0	0	0	71	(425)	518
Deconsolidation of API (see Note 3)			14
Balance at end of year	0	0	0	(113)	(184)	241	0	(113)
Cumulative translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	(16,207)	(17,580)	(25,166)	(23,970)	(22,173)	(23,476)	(25,166)	(23,476)
Other comprehensive income (loss)	1,379	1,373	(2,936)	(2,401)	(1,797)	1,303
Deconsolidation of API (see Note 3)			10,522
Balance at end of year	(14,828)	(16,207)	(17,580)	(26,371)	(23,970)	(22,173)	(14,828)	(26,371)
Change in net pension and other benefit obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	(159,023)	(159,023)	(165,968)	(153,217)	(153,217)	(153,217)	(165,968)	(153,217)
Other comprehensive income (loss)	0	0	0	0	0	0
Deconsolidation of API (see Note 3)			6,945
Balance at end of year	(159,023)	(159,023)	(159,023)	(153,217)	(153,217)	(153,217)	(159,023)	(153,217)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year	(175,504)	(176,877)	(191,422)	(177,645)	(175,423)	(177,244)	(191,422)	(177,244)
Other comprehensive income (loss)	1,379	1,373	(2,936)	(2,330)	(2,222)	1,821
Deconsolidation of API (see Note 3)			17,481
Balance at end of year	$ (174,125)	$ (175,504)	$ (176,877)	$ (179,975)	$ (177,645)	$ (175,423)	$ (174,125)	$ (179,975)