Other Comprehensive Income (Loss) and Related Tax Effects (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Other comprehensive income, tax (expense) benefit
Tax effects on unrealized gains or losses on available-for-sale securities			$ 0	$ 0
Tax effects on foreign currency translation adjustments			0	0
Cumulative foreign currency translation losses	$ (153,800,000)		(153,800,000)		$ (119,400,000)
Unrecognized Tax Benefits, Increase Resulting from Foreign Currency Translation		$ 4,300,000		7,300,000
Reclassifications out of accumulated other comprehensive loss
Total reclassifications, net of tax and noncontrolling interests	(3,000)	(2,000)	(3,000)	540,000
Reclassification out of Accumulated Other Comprehensive Loss | Recognition of realized gains on available-for-sale securities in net income (loss)
Reclassifications out of accumulated other comprehensive loss
Gains (losses) on investments, net	(3,000)	(2,000)	(3,000)	(2,758,000)
Other-than-temporary impairment loss on available-for-sale securities	$ 0	$ 0	$ 0	$ 3,298,000