Subsequent Events Subsequent Events (Details) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2014 Tilda [Member] USD ($)	Mar. 31, 2014 Tilda [Member] GBP (£)	Dec. 31, 2013 Tilda [Member] USD ($)	Jan. 13, 2014 Tilda [Member] USD ($)
Business Acquisition [Line Items]
Revenues	$ 534,879	$ 455,319	$ 1,012,363	$ 815,126			$ 190,000
Payments to Acquire Businesses, Gross					176,325	107,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares					1,646,173	1,646,173
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	102,636		102,636					150,641
Business Combination, Consideration Transferred, Liabilities Incurred						£ 20,000