Acquisitions (Purchase Price Allocation) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of allocated purchase price paid to fair value of acquired net assets for acquisitions
Goodwill	$ 668,129	$ 518,743
2014 [Member]
Schedule of allocated purchase price paid to fair value of acquired net assets for acquisitions
Accounts receivable	67,262
Other current assets	6,610
Property and equipment	31,151
Goodwill	149,592
Customer relationship intangible assets	39,000
Other noncurrent assets	242
Accounts payable and other liabilities	(61,831)
Total	232,026
2013 [Member]
Schedule of allocated purchase price paid to fair value of acquired net assets for acquisitions
Accounts receivable	22,666
Other current assets	922
Property and equipment	14,392
Goodwill	78,646
Customer relationship intangible assets	19,727
Other noncurrent assets	12
Accounts payable and other liabilities	(35,706)
Total	$ 100,659