| Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] |
| | | | | | | | | | | | | | | | | (in thousands) | Currency translation gain (loss) (net of tax) | Net unrealized gain (loss) on investments (net of tax) | Net unrealized gain (loss) on derivative instruments (net of tax) | Net unrecognized gain (loss) related to benefit plans (net of tax) | Total | Balance at December 31, 2016 | $ | (43,987 | ) | $ | (37 | ) | $ | 802 |
| $ | 6,740 |
| $ | (36,482 | ) | Other comprehensive income (loss) before reclassifications | 5,417 |
| 61 |
| 4,587 |
| (44 | ) | 10,021 |
| Amounts reclassified from AOCI to net income (loss) | — |
| (27 | ) | (3,843 | ) | (882 | ) | (4,752 | ) | Net current-period other comprehensive income (loss) | 5,417 |
| 34 |
| 744 |
| (926 | ) | 5,269 |
| Balance at March 31, 2017 | $ | (38,570 | ) | $ | (3 | ) | $ | 1,546 |
| $ | 5,814 |
| $ | (31,213 | ) | Other comprehensive income (loss) before reclassifications | 6,757 |
| (19 | ) | (2,204 | ) | (97 | ) | 4,437 |
| Amounts reclassified from AOCI to net income (loss) | — |
| (1 | ) | (658 | ) | (800 | ) | (1,459 | ) | Net current-period other comprehensive income (loss) | 6,757 |
| (20 | ) | (2,862 | ) | (897 | ) | 2,978 |
| Balance at June 30, 2017 | (31,813 | ) | (23 | ) | (1,316 | ) | 4,917 |
| (28,235 | ) | Other comprehensive income (loss) before reclassifications | 2,591 |
| 69 |
| 268 |
| (66 | ) | 2,862 |
| Amounts reclassified from AOCI to net income (loss) | — |
| (4 | ) | 3,567 |
| (630 | ) | 2,933 |
| Net current-period other comprehensive income (loss) | 2,591 |
| 65 |
| 3,835 |
| (696 | ) | 5,795 |
| Balance at September 30, 2017 | $ | (29,222 | ) | $ | 42 |
| $ | 2,519 |
| $ | 4,221 |
| $ | (22,440 | ) |
| | | | | | | | | | | | | | | | | (in thousands) | Currency translation gain (loss) (net of tax) | Net unrealized gain (loss) on investments (net of tax) | Net unrealized gain (loss) on derivative instruments (net of tax) | Net unrecognized gain (loss) related to benefit plans (net of tax) | Total | Balance at December 31, 2015 | $ | (19,493 | ) | $ | (44 | ) | $ | 1,786 |
| $ | (1,102 | ) | $ | (18,853 | ) | Other comprehensive income (loss) before reclassifications | 1,740 |
| 18 |
| 2,576 |
| (61 | ) | 4,273 |
| Amounts reclassified from AOCI to net income (loss) | — |
| 1 |
| (1,003 | ) | 61 |
| (941 | ) | Net current-period other comprehensive income | 1,740 |
| 19 |
| 1,573 |
| — |
| 3,332 |
| Balance at March 31, 2016 | $ | (17,753 | ) | $ | (25 | ) | $ | 3,359 |
| $ | (1,102 | ) | $ | (15,521 | ) | Other comprehensive income (loss) before reclassifications | (11,566 | ) | (7 | ) | 778 |
| 37 |
| (10,758 | ) | Amounts reclassified from AOCI to net income (loss) | — |
| — |
| (651 | ) | 58 |
| (593 | ) | Net current-period other comprehensive income (loss) | (11,566 | ) | (7 | ) | 127 |
| 95 |
| (11,351 | ) | Balance at June 30, 2016 | (29,319 | ) | (32 | ) | 3,486 |
| (1,007 | ) | (26,872 | ) | Other comprehensive income (loss) before reclassifications | 2,811 |
| 18 |
| 1,132 |
| (25 | ) | 3,936 |
| Amounts reclassified from AOCI to net income (loss) | — |
| — |
| (1,247 | ) | 8 |
| (1,239 | ) | Net current-period other comprehensive income (loss) | 2,811 |
| 18 |
| (115 | ) | (17 | ) | 2,697 |
| Balance at September 30, 2016 | $ | (26,508 | ) | $ | (14 | ) | $ | 3,371 |
| $ | (1,024 | ) | $ | (24,175 | ) |
The amounts reclassified out of AOCI by component and the affected condensed consolidated statements of operations line items are as follows (in thousands): | | | | | | | | | | | | | | | | AOCI component | Line items in the Condensed Consolidated Statements of Operations affected by reclassifications from AOCI | Three months ended September 30, | | Nine months ended September 30, | 2017 | 2016 | | 2017 | 2016 | Derivative financial instruments | Revenues | $ | 2,092 |
| $ | 1,940 |
| | $ | 8,094 |
| $ | 4,524 |
| | Cost of operations | 159 |
| 24 |
| | 113 |
| 57 |
| | Other-net | (7,930 | ) | (445 | ) | | (7,438 | ) | (1,065 | ) | | Total before tax | (5,679 | ) | 1,519 |
| | 769 |
| 3,516 |
| | Provision for income taxes | (2,112 | ) | 272 |
| | (165 | ) | 615 |
| | Net income | $ | (3,567 | ) | $ | 1,247 |
| | $ | 934 |
| $ | 2,901 |
| | | | | | | | Amortization of prior service cost on benefit obligations | Cost of operations | $ | 619 |
| $ | (15 | ) | | $ | 2,281 |
| $ | 294 |
| | Provision for income taxes | (11 | ) | (7 | ) | | (31 | ) | 421 |
| | Net income (loss) | $ | 630 |
| $ | (8 | ) | | $ | 2,312 |
| $ | (127 | ) | | | | | | | | Realized gain on investments | Other-net | $ | 6 |
| $ | — |
| | $ | 50 |
| $ | (1 | ) | | Provision for income taxes | 2 |
| — |
| | 18 |
| — |
| | Net income (loss) | $ | 4 |
| $ | — |
| | $ | 32 |
| $ | (1 | ) |
|