Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,719,709	$ 1,429,517	$ 1,217,536
Total other comprehensive income (loss)	1,293	16,257	8,346
Balance at end of period	1,855,900	1,719,709	1,429,517
Defined Benefit Pension
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	6,303	1,138
Other comprehensive income (loss) before reclassifications	(1,908)	5,075
Amounts reclassified from accumulated other comprehensive income (loss)	(1,736)	90
Total other comprehensive income (loss)	(3,644)	5,165
Balance at end of period	2,659	6,303	1,138
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	16,216	5,124
Other comprehensive income (loss) before reclassifications	4,937	11,092
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Total other comprehensive income (loss)	4,937	11,092
Balance at end of period	21,153	16,216	5,124
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	22,519	6,262
Other comprehensive income (loss) before reclassifications	3,029	16,167
Amounts reclassified from accumulated other comprehensive income (loss)	(1,736)	90
Total other comprehensive income (loss)	1,293	16,257
Balance at end of period	$ 23,812	$ 22,519	$ 6,262