Variable Interest Entities - Number of FG VIE's Consolidated (Details) - Variable Interest Entity, Primary Beneficiary [Member] - Entity	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of FG VIEs Consolidated [Roll Forward]
Number of FG VIE's Consolidated, Beginning of year	32	32	34
Number of FG VIE's consolidated	0	2	1
Number of FG VIE's deconsolidated	(1)	(2)	(2)
Number of FG VIE's matured	0	0	(1)
Number of FG VIE's Consolidated, December 31	31	32	32