Concentration Risk Voluntary Fee Waivers (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Revenue	$ 0	$ (10)	$ (144)	$ (4,262)	$ (11,027)	$ (18,030)	$ (21,333)	$ (37,482)	$ (4,400)	$ (87,800)	$ (333,600)
Less: Reduction in Distribution expense	(2)	(1)	99	3,490	7,627	13,797	16,528	27,896	3,600	65,800	240,600
Operating income	(2)	(11)	(45)	(772)	(3,400)	(4,233)	(4,805)	(9,586)	(800)	(22,000)	(93,000)
Less: Reduction in Noncontrolling interest	0	0	0	0	0	0	(208)	208	0	0	7,100
Pre-tax impact	$ (2)	$ (11)	$ (45)	$ (772)	$ (3,400)	$ (4,233)	$ (5,013)	$ (9,378)	$ (800)	$ (22,000)	$ (85,900)