Supplemental Balance Sheet, Income Statement and Cash Flow Information - Accumulated Other Comp Inc (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	$ 3,247,025
Other comprehensive income (loss), net of tax	23,304	$ 35,474	$ (125,115)
Balance at the end of the period	2,911,816	3,247,025
Accumulated Other Comprehensive Income
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	(12,119)	(47,593)
Other comprehensive income (loss) before reclassifications	22,311	28,797
Amounts reclassified from accumulated other comprehensive income (loss)	993	6,677
Other comprehensive income (loss), net of tax	23,304	35,474
Balance at the end of the period	11,185	(12,119)	(47,593)
Gains (losses) on cash flow hedges
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	(1,296)	(1,670)
Amounts reclassified from accumulated other comprehensive income (loss)	374	374
Other comprehensive income (loss), net of tax	374	374
Balance at the end of the period	(922)	(1,296)	(1,670)
Unrealized gains (losses) on available-for-sale securities
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	14,235	(314)
Other comprehensive income (loss) before reclassifications	(6,061)	11,054
Amounts reclassified from accumulated other comprehensive income (loss)	970	3,495
Other comprehensive income (loss), net of tax	(5,091)	14,549
Balance at the end of the period	9,144	14,235	(314)
Defined benefit pension plan items
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	(3,760)	(6,568)
Amounts reclassified from accumulated other comprehensive income (loss)	(351)	2,808
Other comprehensive income (loss), net of tax	(351)	2,808
Balance at the end of the period	(4,111)	(3,760)	(6,568)
Foreign currency items
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period	(21,298)	(39,041)
Other comprehensive income (loss) before reclassifications	28,372	17,743
Other comprehensive income (loss), net of tax	28,372	17,743
Balance at the end of the period	$ 7,074	$ (21,298)	$ (39,041)