Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 93,461	$ 68,034	$ 70,315	$ 66,088
Additions based on tax positions related to the current year	15,580	14,466	7,929
Additions for tax positions of prior years	29,637	4,105	9,076
Reductions for tax positions of prior years	(5,226)	(9,653)	(3,067)
Settlements	(7,345)	(954)	(3,106)
Lapse of statutes	(7,219)	(10,245)	(6,605)
Unrecognized potential tax benefits that would impact effective tax rate	85,400
Potential interest and penalty expense (income)	2,400	(500)	$ 700
Accrued interest and penalties	18,800	$ 16,500
Minimum [Member]
Income Tax Contingency [Line Items]
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound	0
Maximum [Member]
Income Tax Contingency [Line Items]
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound	$ 12,500