Basis and Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification out of accumulated other comprehensive income (loss)			$ 0
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			1,481,598,000
Other Comprehensive Income	$ 782,000	$ (241,000)	1,431,000	$ 445,000
Ending balance	1,573,956,000		1,573,956,000
Foreign Currency
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			(531,000)
Other Comprehensive Income			1,431,000
Ending balance	$ 900,000		$ 900,000