Stockholders' Equity (Details Textual) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($) shares	Mar. 31, 2015 USD ($) shares	Jan. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) CustomerAccount shares	Dec. 31, 2015 USD ($) CustomerAccount $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Feb. 28, 2015 shares
Stockholders Equity Transaction [Line Items]
Increase in number of shares authorized for repurchase								7,500,000
Number of shares authorized for repurchase under stock repurchase program								42,500,000
Repurchase of common stock, shares					1,800,000
Total amount paid | $					$ 65,027	$ 26,033	$ 15,478
Remaining number of shares available for repurchase	7,100,000				7,100,000
Repurchase of common stock for employee tax withholdings, shares					265,000	252,000	264,000
Repurchase of common stock for tax withholdings, value | $					$ 8,100	$ 6,900	$ 5,400
Cash dividends declared per common share | $ / shares					$ 0.70	$ 0.6225	$ 0.45
Cash dividend | $					$ 22,900	$ 21,300
Stock warrants term						10 years
Stock warrants, exercise price | $ / shares						$ 26.68
Additional number of Residential Customer Accounts migrated | CustomerAccount					5,000,000
Senior Subordinated Convertible Notes 2010
Stockholders Equity Transaction [Line Items]
Carrying amount of the equity component of convertible debt securities outstanding | $	$ 22,900			$ 22,900	$ 22,900	$ 22,900
Migration Of Comcast Current Residential Customer Accounts
Stockholders Equity Transaction [Line Items]
Issuance of stock warrants				1,900,000		1,900,000
Number of customer account migrated | CustomerAccount				2,000,000
Migration Of Comcast Current Residential Customer Accounts | First 25 % of Stock Warrants
Stockholders Equity Transaction [Line Items]
Vesting percentage of stock warrants				25.00%
Number of customer account migrated | CustomerAccount				500,000
Number of stock warrants vesting				500,000
Fair value of stock warrants vesting | $				$ 3,600
Migration Of Comcast Current Residential Customer Accounts | Second 25 % of Stock Warrants
Stockholders Equity Transaction [Line Items]
Vesting percentage of stock warrants			25.00%
Vesting date of stock warrants					2015-01
Fair value of stock warrants vesting | $			$ 3,700
Migration Of Comcast Current Residential Customer Accounts | Third 25 % of Stock Warrants
Stockholders Equity Transaction [Line Items]
Vesting percentage of stock warrants					25.00%
Number of customer account migrated | CustomerAccount					5,500,000
Migration Of Comcast Current Residential Customer Accounts | Last 25 % of Stock Warrants
Stockholders Equity Transaction [Line Items]
Vesting percentage of stock warrants					25.00%
Additional number of Residential Customer Accounts migrated | CustomerAccount					5,700,000
Total target of customer account migrations | CustomerAccount					11,200,000
Migration Of Comcast Current Residential Customer Accounts | Last 25 % of Stock Warrants | Minimum
Stockholders Equity Transaction [Line Items]
Number of customer account migrated | CustomerAccount					5,500,000
Migration Of Comcast Acquired Additional Residential Customer Accounts
Stockholders Equity Transaction [Line Items]
Issuance of stock warrants				1,000,000		1,000,000
Comcast
Stockholders Equity Transaction [Line Items]
Issuance of stock warrants				2,900,000		2,900,000
Amount of unvested stock warrants that become vested upon a fundamental change of the Company					50.00%
Beneficial ownership required for potential cash settlement	19.99%				19.99%
Stock warrants exercised					0
Comcast | Stock Warrants
Stockholders Equity Transaction [Line Items]
Client contract incentive related to stock warrants | $	$ 7,300				$ 7,300
Amortization expense of client contract incentive related to stock warrants | $	2,000				$ 2,000
SEC Rule 10b5-1 Plan
Stockholders Equity Transaction [Line Items]
Repurchase of common stock, shares					300,000	700,000	500,000
Total amount paid | $					$ 6,900	$ 19,100	$ 10,100
Weighted-average price per share | $ / shares					$ 27.06	$ 26.05	$ 20.23
ASR Agreement
Stockholders Equity Transaction [Line Items]
Repurchase of common stock, shares		1,300,000			1,600,000
Total amount paid | $	$ 10,000	$ 40,000
Weighted-average price per share | $ / shares					$ 31.64
Accelerated share repurchase agreement, total amount paid | $		$ 50,000