Income Taxes (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 13,320	$ 10,634	$ 8,560
Tax positions taken during prior periods	1,141	0	1,691
Tax positions taken during the current period	778	117	0
Acquisition	0	2,569	598
Settlements	(4,162)	0	0
Lapse of the applicable statute of limitations	(1,868)	0	(215)
Balance at December 31	9,209	13,320	10,634
Interest and penalties	(257)	(337)	616
The liability for unrecognized tax benefits included accrued interest	$ 1,576	$ 1,838	$ 1,923