Share-based Compensation - Allocation of Share-based Compensation Expense and Additional Disclosures (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 15,438	$ 8,122	$ 15,328
Share based compensation expense per share, basic (in usd per share)	$ 0.20	$ 0.11	$ 0.20
Share based compensation expense per share, diluted (in usd per share)	$ 0.20	$ 0.11	$ 0.20
Cost of Service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	724	254	1,734
Selling and Marketing Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	830	22	1,985
General and Administrative Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 13,884	$ 7,846	$ 11,609