Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Non-cash investing and financing activities:
Fixed assets acquired with accounts payable or accrued liabilities	$ 12,202	$ 20,854
Conversion of convertible notes receivable into equity securities	0	4,862
Issuance of promissory note in exchange for sale of equity method investment	54,154	0
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	9,020
Investing cash flows from finance leases	10,896
Financing cash flows from finance leases	45,773	$ 0
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	21,066
Finance leases	$ 51,064