Acquisitions - Reconciliation of Aggregate Purchase Price of Acquisitions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Business Acquisition [Line Items]
Acquisitions - cash plaid (net of cash acquired)	$ 170,604,000	$ 109,928,000	$ 0
Other payments to acquire businesses, restricted cash	$ 25,625,000	$ 14,363,000	$ 0
Nubera and Capterra
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%			100.00%
Aggregate purchase price	$ 206,900,000
Cash Acquired from Acquisition	(10,700,000)
Acquisitions - cash plaid (net of cash acquired)	196,200,000
Acquisitions cash place in escrow	30,000,000
Contingent consideration arrangements, maximum value (up to)	32,000,000
Capterra
Business Acquisition [Line Items]
Aggregate purchase price	179,200,000
Nubera
Business Acquisition [Line Items]
Aggregate purchase price	27,700,000
Other Noncurrent Assets | Nubera and Capterra
Business Acquisition [Line Items]
Other payments to acquire businesses, restricted cash	$ 25,600,000