Income Taxes (Unrecognized tax benefits - rollforward and discussion) (Details) - 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, beginning of period	$ 23,149	$ 23,332	$ 12,670
Additions based on tax positions related to the current year	1,419	1,822	12,727
Additions for tax positions of prior years	2,661	689	3,341
Reductions for tax positions of prior years	(1)	(2,589)	(4,815)
Reductions from lapse of statutes of limitations	(17)	(105)	(591)
Balance, end of period	27,211	$ 23,149	$ 23,332
Income tax contingency [Abstract]
Unrecognized tax benefits, period increase (decrease)	4,100
Liability for uncertain tax positions	24,800
Accrued and unpaid interest and penalties	$ 4,200