Profit Sharing Plan and Annual Cash Bonuses (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangements [Abstract]
Maximum percentage of compensation employee is allowed to contribute	15.00%
Matching contributions	$ 9,000,000	$ 8,600,000	$ 8,200,000
Bonus expense, cash	$ 0	$ 0	$ 16,800,000

Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration