Restructuring Charges (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012 contract
Restructuring Cost and Reserve [Line Items]
Number of service contracts assigned to third parties			2
Costs incurred and charged to expense	$ 4,992	$ 5,765	$ 15,225
Restructuring Reserve [Roll Forward]
Accrued liability beginning balance	756	2,431	131
Costs incurred and charged to expense	4,992	3,961	11,929
Cash payments	(5,299)	(5,636)	(9,629)
Accrued liability ending balance	449	756	2,431
Employee Separation Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred and charged to expense	4,992	3,961	9,052
Restructuring Reserve [Roll Forward]
Accrued liability beginning balance	756	731	131
Costs incurred and charged to expense	4,992	3,961	8,300
Cash payments	(5,299)	(3,936)	(7,700)
Accrued liability ending balance	449	756	731
Contract Assignment Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred and charged to expense	0	0	3,629
Restructuring Reserve [Roll Forward]
Accrued liability beginning balance	0	1,700	0
Costs incurred and charged to expense	0	0	3,629
Cash payments	0	(1,700)	(1,929)
Accrued liability ending balance	0	0	1,700
Asset Related and Other Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred and charged to expense	$ 0	$ 1,804	$ 2,544