Variable Interest Entities - Additional Information (Details) $ in Thousands	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Variable Interest Entity [Line Items]
Assets	$ (43,573,902)	$ (44,686,703)
Total equity	$ (3,511,040)	(3,333,231)	$ (3,113,968)	$ (4,051,734)
Number of consolidated entities	5
Non-marketable and other securities	$ 668,497	674,946
Maximum exposure to loss in unconsolidated VIEs	362,470	364,450
Consolidated
Variable Interest Entity [Line Items]
Assets	(208,258)	(216,019)
Non-marketable and other securities	196,789	203,714
Maximum exposure to loss in unconsolidated VIEs	207,700
Low Income Housing Tax Credit Funds | Consolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	157,700	154,400
Unfunded commitments | Consolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	$ 87,800	$ 91,000