Summary of Significant Accounting Policies - Allowance for Doubtful Accounts and Credit Memo Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation Allowance [Line Items]
The general period to charge-off uncollectible balances of receivable, as circumstances warrant, is no later than this period of time past due	1 year
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of the Year	$ 31,447	$ 32,141	$ 34,645
Credit Memos Charged to Revenue	37,616	42,497	47,137
Allowance for Bad Debts Charged to Expense	8,705	15,326	14,209
Other	16,528	(4,511)	(572)
Deductions	(50,006)	(54,006)	(63,278)
Balance at End of the Year	$ 44,290	$ 31,447	$ 32,141