Stockholders Equity and Equity Compensation Plans (Details Textual) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended			0 Months Ended		0 Months Ended	9 Months Ended
	Jul. 25, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Performance Shares	Sep. 30, 2014 Restricted common stock Maximum	Sep. 30, 2014 Restricted common stock Maximum	Sep. 30, 2014 Restricted common stock Minimum	Sep. 30, 2014 Restricted common stock Minimum	May 22, 2014 Stock Incentive Plan 2005	Sep. 30, 2014 Stock Incentive Plan 2005	Dec. 31, 2013 Stock Incentive Plan 2005	Jul. 25, 2014 Migration Of Comcast Current Residential Customer Accounts	Jul. 25, 2014 Migration Of Comcast Acquired Additional Residential Customer Accounts	Jul. 25, 2014 Comcast	Sep. 30, 2014 Comcast
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares repurchased				0.2	0.5
Total amount paid				$ 5.2	$ 10.1
Weighted-average price per share				$ 27.26	$ 20.23
Remaining number of shares available for repurchase		1.9		1.9
Repurchase of common stock for employee tax withholdings, shares				0.2	0.3
Repurchase of common stock for tax withholdings, value				6.7	5.0
Cash dividends declared per common share		$ 0.1575	$ 0.1500	$ 0.4650	$ 0.3000
Cash dividend		5.5	5.1
Payment of cash dividends common stock				16.0	10.2
Date of Dividend Approval				Jun. 30, 2013
Issuance of stock warrants														1.9	1.0	2.9
Stock warrants term	10 years
Stock warrants, exercise price	$ 26.68	$ 26.68
Initial vesting percentage of stock warrants														25.00%
Number of stock warrants vesting														0.5
Vesting date of stock warrants														2015-01
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%
Fair value of stock warrants vesting in January 2015														3.7
Client contract incentive related to stock warrants																	1.2
Amortization expense of client contract incentive related to stock warrants																	0.1
Number of increased authorized shares under incentive plan											2.9
Number of authorized shares under incentive plan												18.7	15.8
Performance based awards granted to executive management shares						0.1
Common stock shares issued to members of executive management vesting installments						3 years	3 years	3 years	4 years	4 years
Stock-based compensation expense		$ 4.5	$ 4.0	$ 12.3	$ 11.5