Equity, Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated net income	$ 96,200,000	$ 83,700,000	$ 115,500,000	$ 129,600,000	$ 190,100,000	$ 134,300,000	$ 130,300,000	$ 164,600,000	$ 425,012,000	$ 619,373,000	$ 115,228,000
Other Comprehensive Income (Loss), Net of Tax:
Change in net unrealized (loss) gain on investments, net									(9,900,000)	(300,000)	(2,800,000)
Change in foreign currency translation adjustment, net									(6,400,000)	500,000	5,600,000
Total other comprehensive income (loss), net									(16,300,000)	200,000	2,800,000
Consolidated comprehensive income									408,700,000	619,600,000	118,000,000
Adjust for comprehensive loss (income) attributable to noncontrolling interest									100,000	(1,000,000)	1,800,000
Comprehensive income attributable to Juniper Networks									$ 408,800,000	$ 618,600,000	$ 119,800,000