Segment Information, Reconciliation of Total Segment Profits to Consolidated Totals (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reconciliation of total segment profits to the Company's consolidated totals [Abstract]
Net income	$ 15,080	$ 17,678
Net loss attributable to non-controlling interest in subsidiaries	(40)	(65)
Net income attributable to controlling interest	15,120	17,743
Reportable Segments [Member]
Reconciliation of total segment profits to the Company's consolidated totals [Abstract]
Net income	14,909	16,983
Intersegment Eliminations [Member]
Reconciliation of total segment profits to the Company's consolidated totals [Abstract]
Net income	$ 171	$ 695