Restricted Cash and Short-term Investments (Tables)

6 Months Ended

Jun. 30, 2018

Table Text Blocks

Schedule of short-term investments

		Gross	Gross	Fair Value
	Amortized	Unrealized	Unrealized	(Net Carrying
	Cost	Gains	Losses	Amount)
	$	$	$	$
U.S. treasury securities	902,771	644	—	903,415
U.S. agency securities	17,612	9	—	17,621
Time deposits	10,172	—	—	10,172
Total	930,555	653	—	931,208

Short-term investments as of December 31, 2017 consisted of the following available-for-sale debt securities and time deposits:

		Gross	Gross	Fair Value
	Amortized	Unrealized	Unrealized	(Net Carrying
	Cost	Gains	Losses	Amount)
	$	$	$	$
U.S. treasury securities	561,733	—	406	561,327
U.S. agency securities	17,651	12	—	17,663
Time deposits	18,924	—	—	18,924
Total	598,308	12	406	597,914