Other Balance Sheet Amounts - Accrued Expenses (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued compensation	$ 23,642,000		$ 31,799,000
Accrued commissions	9,387,000		13,856,000
Accrued interest	8,625,000		8,625,000
Other accrued expenses	16,031,000		14,051,000
Total accrued expenses	57,685,000		$ 68,331,000
Amortization of expenses from commissions paid to sales force	17,400,000	$ 19,500,000
Impairment cost in relation to costs capitalized	$ 0	$ 0