Income Taxes (Deferred Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	$ 37,214	$ 32,142
Deferred tax liabilities, gross	24,134	19,749
Valuation allowance	0	0
Deferred tax assets, net of valuation allowance	37,214	32,142
Deferred tax liabilities, net	24,134	19,749
Depreciation and amortization [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	102	331
Deferred tax liabilities, gross	0	277
Share-based compensation [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	721	549
Deferred tax liabilities, gross	0	0
Accruals and prepaids [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	1,627	2,009
Deferred tax liabilities, gross	239	297
Bad Debts [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	446	720
Deferred tax liabilities, gross	0	0
Acquired intangible assets [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	0	933
Deferred tax liabilities, gross	23,895	19,175
Net operating loss carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	20,573	22,237
Deferred tax liabilities, gross	0	0
Tax credit carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Total deferred income tax assets	13,745	5,363
Deferred tax liabilities, gross	$ 0	$ 0