Lease and Financing Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Building [Abstract]
Value of New Building	$ 678,457	$ 666,130
Accumulated depreciation	233,725	211,593
Deposit paid to landlord	38,858	39,016
Operating Leases, Minimum Future Obligations [Abstract]
2017	36,180
2018	30,001
2019	21,310
2020	11,602
2021	5,997
Thereafter	15,127
Total	120,217
Financing Obligations, Minimum Future Obligations [Abstract]
2017	631
2018	650
2019	670
2020	690
2021	698
Thereafter	2,502
Total minimum lease payments	5,841
Rent expense for operating leases	48,200	52,400	$ 52,300
Interest expense associated with financing obligation	$ 200	100	$ 0
New Regional Headquarters Building [Member]
New Building [Abstract]
Extension period for lease	10 years
Initial term of lease	10 years
Value of New Building	$ 18,900	19,900
Accumulated depreciation	800	300
Financing obligation	10,000	10,600
Deposit paid to landlord	9,100	9,300
Tenant incentive asset	4,900	5,600
Deferred tenant incentive liability	$ 4,500	$ 5,100
Office Space and Computer Hardware [Member]
New Building [Abstract]
Extension period for lease	3 years