Supplemental Cash Flow Information - Restrictions on Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 212,340	$ 334,884	$ 322,833
Restricted cash	14,053	12,434	13,092
Total cash, cash equivalents and restricted cash	$ 226,393	$ 347,318	$ 335,925	$ 434,384