Commitments and Contingencies (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Rental expense for operating leases	$ 2,100,000	$ 2,400,000	$ 6,700,000	$ 7,600,000
Defined benefit plan employer matching contribution on first five percent of employee compensation			50.00%
Percentage of employees' eligible compensation for employer matching contribution			5.00%
Defined benefit plan employer contribution limit			$ 6,000
Defined benefit plan employer contribution vesting period			5 years
Defined benefit plan employer contribution	300,000	$ 300,000	$ 1,100,000	$ 1,000,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Proceeds from amounts drawn against letters of credit	0		0
Letter of Credit [Member] | LOC for Office Space [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding	1,900,000		1,900,000
Letter of Credit [Member] | LOC for Security Deposit [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 100,000		$ 100,000