Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,855,900	$ 1,719,709
Total other comprehensive income (loss)	(2,356)	15,052
Balance at end of period	1,832,582	1,747,074
Defined Benefit Pension
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	2,659	6,303
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	(132)	(39)
Total other comprehensive income (loss)	(132)	(39)
Balance at end of period	2,527	6,264
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	21,153	16,216
Other comprehensive income (loss) before reclassifications	(2,224)	15,091
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Total other comprehensive income (loss)	(2,224)	15,091
Balance at end of period	18,929	31,307
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	23,812	22,519
Other comprehensive income (loss) before reclassifications	(2,224)	15,091
Amounts reclassified from accumulated other comprehensive income (loss)	(132)	(39)
Total other comprehensive income (loss)	(2,356)	15,052
Balance at end of period	$ 21,456	$ 37,571