Income Taxes (Deferred Income Taxes) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	$ 63,326	$ 57,941
Valuation allowance	(35)	(3,747)
Deferred tax assets, net of valuation allowance	63,291	54,194
Deferred tax liabilities, gross	19,421	22,508
Deferred tax liabilities, net	19,421	22,508
Depreciation and amortization
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	683	95
Deferred tax liabilities, gross	0	0
Share-based compensation
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	590	1,612
Deferred tax liabilities, gross
Accruals and prepaids
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	2,700	842
Deferred tax liabilities, gross
Bad Debts
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	1,076	859
Deferred tax liabilities, gross
Acquired intangible assets
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	0	0
Deferred tax liabilities, gross	19,421	22,508
Net operating loss carryforwards
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	15,233	19,019
Deferred tax liabilities, gross
Tax credit carryforwards
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	43,044	35,514
Deferred tax liabilities, gross