Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 04, 2016 USD ($)
Advertising Expense	$ 222,067	$ 210,929	$ 178,068
Foreign Currency Transaction Gain (Loss), before Tax	38,951	21,990	$ 23,729
Accounts Receivable, Net, Noncurrent	$ 114,258	$ 79,048
Stockholders entitled election of Board of Directors	25.00%
Stock Repurchase Program, Authorized Amount				$ 500,000
Treasury Stock Acquired, Average Cost Per Share | $ / shares	$ 54.19
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 276,763
Common Class A [Member]
Common Stock, Voting Rights	1
Common Stock, Conversion Basis	1
Share repurchases | shares	(4,119,558)
Common Class B [Member]
Common Stock, Voting Rights	10
Common Stock, Conversion Basis	1
Share repurchases | shares	0
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Number of Customers	1	1
Concentration Risk, Percentage	19.00%	17.00%
Maximum [Member]
Deferred Carriage Fees Contractual Period	13 years
Restricted Stock Units (RSUs) [Member] | 2011 Non-Employee Director Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%