Lease Obligations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Leases [Abstract]
Future minimum lease payment - due in 2016	$ 42,470,000
Future minimum lease payment - due in 2017	39,443,000
Future minimum lease payment - due in 2018	35,286,000
Future minimum lease payment - due in 2019	30,941,000
Future Minimum Payments, Due in 2020	28,584,000
Future minimum lease payment - due thereafter	105,825,000
Rental expense	$ 46,271,000	$ 45,198,000	$ 44,752,000