Summary of Significant Accounting Policies - Deferred Costs & Impairment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Summary of Significant Accounting Policies
Impairment loss related to intangible assets	$ 0	$ 0	$ 0	$ 0
Goodwill	40,646		40,646		$ 41,191
Impairment loss related to goodwill	0	0	0	0
Reduction of goodwill	500		500
Deferred Costs
Internal sales commissions	17,976		17,976		18,748
Third party commissions	12,167		12,167		13,643
External legal counsel	800		800		730
Total	30,943		30,943		$ 33,121
Recoverability of Long-Lived Assets
Impairment of real estate	$ 0	$ 0	$ 0	$ 0