Employment Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefits [Abstract]
Matching contributions	$ 5,700,000	$ 6,400,000	$ 5,700,000
Minimum [Member]
Employee Benefits [Abstract]
Employee contribution limit per calendar year	19,500
Maximum [Member]
Employee Benefits [Abstract]
Employee contribution limit per calendar year	$ 26,000