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Accounting for Stock-based Compensation - Summary of Non-employee Director Awards Activity (Details) - Non-Employee Director Awards - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted			7,985
Weighted-Average Grant Date Fair Value, Granted			$ 60.36
Omnibus Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Non-vested Beginning Balance	4,860	4,968
Number of Shares, Granted	12,541	9,732	11,606
Number of Shares, Vested	(10,891)	(9,840)	(5,395)
Number of Shares, Cancelled			(1,243)
Number of Shares, Non-vested Ending Balance	6,510	4,860	4,968
Number of Shares, expected to vest in the future	6,510
Weighted-Average Grant Date Fair Value, Non-vested Beginning Balance	$ 73.94	$ 72.35
Weighted-Average Grant Date Fair Value, Granted	64.58	73.94	$ 72.35
Weighted-Average Grant Date Fair Value, Vested	68.82	73.14	72.35
Weighted-Average Grant Date Fair Value, Cancelled			72.35
Weighted-Average Grant Date Fair Value, Non-vested Ending Balance	64.47	$ 73.94	$ 72.35
Weighted-Average Grant Date Fair Value, expected to vest in the future	$ 64.47
Aggregate Intrinsic Value, Non-vested	$ 483,888
Aggregate Intrinsic Value, expected to vest in the future	$ 483,888

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Amount by which the current fair value of the underlying stock exceeds the exercise price of expected to vest equity instruments (other than options) outstanding.

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