Summary of Significant Accounting Policies - Summary of Reconciliation of Cash, Cash Equivalents, and Restricted Cash Reported in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents, beginning of period	$ 233,711	$ 189,326	$ 252,836
Cash and cash equivalents	272,804	233,711	189,326
Restricted cash	5,825	0	0
Cash, cash equivalents and restricted cash of $5,825, $0 and $0 at end of period	278,629	233,711	189,326
Net increase (decrease) in cash, cash equivalents and restricted cash	$ 44,918	$ 44,385	$ (63,510)