Summary of Significant Accounting Policies - Deferred Costs & Impairment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Summary of Significant Accounting Policies
Impairment loss related to intangible assets	$ 0	$ 0
Goodwill	41,191		$ 41,191
Impairment loss related to goodwill	0	0
Deferred Costs
Internal sales commissions	18,493		18,748
Third party commissions	12,883		13,643
External legal counsel	742		730
Total	32,118		$ 33,121
Recoverability of Long-Lived Assets
Impairment of real estate	$ 0	$ 0