Operations and Summary of Significant Accounting Policies - Revision of Prior Period Financial Statements, Equity Statement (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance retained earnings		$ 1,663,671	$ 1,663,671	$ 1,601,688	$ 1,516,044	$ 1,361,406
Beginning balance - Amount	$ 2,734,755		2,801,321	2,735,993	2,647,071	2,480,308
Ending balance retained earnings	1,655,317		1,663,671	1,663,671	1,601,688	1,516,044
Ending balance - Amount	$ 2,800,404	$ 2,734,755		2,801,321	2,735,993	2,647,071
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance retained earnings			1,694,608	1,623,128	1,537,425	1,381,492
Beginning balance - Amount			2,832,258	2,757,433	2,668,452	2,500,394
Ending balance retained earnings				1,694,608	1,623,128	1,537,425
Ending balance - Amount				2,832,258	2,757,433	2,668,452
Revision of Prior Period, Error Correction, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance retained earnings			(30,937)	(21,440)	(21,381)	(20,086)
Beginning balance - Amount			$ (30,937)	(21,440)	(21,381)	(20,086)
Ending balance retained earnings				(30,937)	(21,440)	(21,381)
Ending balance - Amount				$ (30,937)	$ (21,440)	$ (21,381)