Accrued Expenses and Other Liabilities (Components of Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accrued Expenses and Other Liabilities [Abstract]
Accrued bonuses	$ 15,242	$ 19,480
Accrued commissions and salaries	7,323	8,712
Taxes payable	4,103	4,285
Deferred rent liabilities	4,023	4,200
Lease incentive obligations	3,815	4,099
Unrecognized tax benefit	2,836	3,791
Customer credit balances	2,510	2,573
Accrued health care costs	2,281	2,707
Other liabilities	9,971	9,791
Total accrued expenses and other liabilities	52,104	59,638
Less: Long-term portion	6,747	7,437
Accrued expenses and other current liabilities	$ 45,357	$ 52,201