Acquisitions Acquisitions (Pro Forma) (Details) (USD $)	12 Months Ended				4 Months Ended	12 Months Ended
	Dec. 31, 2013 Two Thousand Thirteen [Member]	Dec. 31, 2012 Two Thousand Thirteen [Member]	Dec. 31, 2012 Two Thousand Twelve [Member]	Dec. 31, 2011 Two Thousand Twelve [Member]	Dec. 31, 2012 Prime [Member]	Dec. 31, 2011 Prime [Member]
Business Acquisition [Line Items]
Revenue of Acquiree since Acquisition Date, Actual	$ 84,300,000		$ 73,700,000		$ 29,900,000
Earnings or Loss of Acquiree since Acquisition Date, Actual	7,700,000		9,000,000		1,400,000
Pro Forma Revenue	1,466,404,000	1,265,698,000	1,185,927,000	1,037,303,000		894,127,000
Pro Forma Net Income (Loss)	$ 49,137,000	$ 37,345,000	$ 38,850,000	$ 28,688,000		$ 28,871,000
Pro Forma Earnings Per Share, Basic						$ 0.94
Pro Forma Earnings Per Share, Diluted						$ 0.91