Stockholders' Equity and Equity Compensation Plans (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2017	Jan. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2014
Stockholders Equity And Equity Compensation Plans [Line Items]
Remaining number of shares available for repurchase			6,500,000		6,500,000
Repurchase of common stock for employee tax withholdings, shares					200,000	300,000
Repurchase of common stock for tax withholdings, value					$ 6,300	$ 10,000
Cash dividends declared per common share			$ 0.1975	$ 0.185
Cash dividend			$ 6,700	$ 6,000	$ 13,400	12,000
Stock warrants term								10 years
Stock warrants, exercise price								$ 26.68
Number of stock warrants vested							1,400,000
Stock warrants issued			1,500,000		1,500,000
Remaining number of stock warrants vested					0
Carrying amount of common stock warrants							$ 16,007
Stock-based compensation expense			$ 6,000	$ 5,600	$ 11,644	$ 12,086
Performance Shares
Stockholders Equity And Equity Compensation Plans [Line Items]
Performance based awards granted to executive management and certain key employees shares					100,000
Vesting period					3 years
Restricted common stock
Stockholders Equity And Equity Compensation Plans [Line Items]
Vesting period			4 years		4 years
Senior Subordinated Convertible Notes 2010
Stockholders Equity And Equity Compensation Plans [Line Items]
Common shares from treasury stock delivered to settle conversion obligation in excess of par value	694,240
Carrying value of shares of treasury stock delivered	$ 16,500
Carrying value of treasury stock delivered, per share	$ 23.71
Conversion obligation in excess of par value	$ 28,800
Common stock Warrants
Stockholders Equity And Equity Compensation Plans [Line Items]
Stock warrants exercised		1,400,000
Common shares from treasury stock delivered to settle conversion obligation in excess of par value		649,221
Fair value of shares of treasury stock delivered		$ 31,500
Carrying value of shares of treasury stock delivered		$ 15,400
Carrying value of treasury stock delivered, per share		$ 23.66
Carrying amount of common stock warrants		$ 16,000
Comcast Corporation
Stockholders Equity And Equity Compensation Plans [Line Items]
Issuance of stock warrants								2,900,000
Stock warrants exercised		1,400,000
Comcast Corporation | Common stock Warrants
Stockholders Equity And Equity Compensation Plans [Line Items]
Client contract incentive related to stock warrants					$ 16,000
Amortization expense of client contract incentive related to stock warrants					$ 6,600
SEC Rule 10b5-1 Plan
Stockholders Equity And Equity Compensation Plans [Line Items]
Repurchase of common stock, shares					300,000	300,000
Total amount paid					$ 10,500	$ 9,500
Weighted-average price per share					$ 41.00	$ 36.07