Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Cash paid for operating lease liabilities	$ 30,504
Income tax refund received	1,176	$ 4,476
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	688,698	363,703
Restricted cash	1,686	1,755
Cash, cash equivalents and restricted cash	690,384	$ 365,458
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 29,257