Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,990,239	$ 1,855,900	$ 1,719,709
Other comprehensive income (loss) before reclassifications	7,943	(4,108)
Amounts reclassified from accumulated other comprehensive income (loss)	212	(589)
Total other comprehensive income (loss)	8,155	(4,697)	1,293
Balance at end of period	2,353,959	1,990,239	1,855,900
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	19,115	23,812	22,519
Total other comprehensive income (loss)	8,155	(4,697)	1,293
Balance at end of period	27,270	19,115	23,812
Defined Benefit Pension (2)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(4,820)	2,659
Other comprehensive income (loss) before reclassifications	394	(6,890)
Amounts reclassified from accumulated other comprehensive income (loss)	208	(589)
Total other comprehensive income (loss)	602	(7,479)
Balance at end of period	(4,218)	(4,820)	2,659
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	23,935	21,153
Other comprehensive income (loss) before reclassifications	7,532	2,782
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Total other comprehensive income (loss)	7,532	2,782
Balance at end of period	31,467	23,935	21,153
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0
Other comprehensive income (loss) before reclassifications	17	0
Amounts reclassified from accumulated other comprehensive income (loss)	4	0
Total other comprehensive income (loss)	21	0
Balance at end of period	$ 21	$ 0	$ 0