Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rental expense	$ 87,500,000	$ 87,300,000	$ 85,900,000
Rodriguez Case
Loss Contingencies [Line Items]
Allegations loss	0
Gentry Case
Loss Contingencies [Line Items]
Allegations loss	$ 0