Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Cumulative effect of changes in accounting		$ (2,715,183)	$ (2,744,082)	$ (2,675,425)	$ (2,480,984)	$ (2,463,651)	$ (2,425,443)	$ (2,442,326)	$ (2,447,660)
Cumulative effect of changes in accounting standard
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of changes in accounting					147				239
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of changes in accounting		$ 627,884	$ 595,117	$ 563,742	$ 529,194	$ 526,195	$ 497,007	$ 460,357	$ 428,307