Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 85,845	$ 69,117	$ 65,290
Gross increases — tax positions of prior periods	2,704	2,692	6,391
Gross increases — current period tax positions	3,021	27,163	6,252
Gross decreases — tax positions of prior periods	(15,287)	(277)	(6,491)
Gross decreases — lapse of applicable statute of limitations	(6,186)	(12,850)	(287)
Gross decreases — settlements	(5,205)	0	(2,038)
Balance at end of year	$ 64,892	$ 85,845	$ 69,117