Fair Value - Level III (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Total realized and unrealized gains (losses):
Included in earnings: Net accretion	$ 4,257	$ 3,373
Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	64,941,714	74,836,009
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	(6,151,427)	(3,852,259)
Included in earnings: Net accretion	3,886	3,415
Included in OCI	1,846	(3,400)
Purchases / Originations	445,887	275,213
Sales	(189,730)	(256,964)
Issuances	(4,759)	(596)
Cash repayments / receipts	(46,987)	(13,401)
Transfers into Level III	(63,970)	(415,044)
Transfers out of Level III	129,452	110,965
Consolidations of VIEs	1,127,952	14,534,280
Deconsolidations of VIEs	(1,517,502)	(2,583,751)
Balance at the end of the period	58,676,362	82,634,467
Amount of total (losses) gains included in earnings attributable to assets still held at period end	(6,156,640)	(3,853,041)
VIE liabilities \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	(2,585,369)	(2,552,448)
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	384,981	236,123
Issuances	(4,759)	(596)
Cash repayments / receipts	(30,796)	5,850
Transfers into Level III	(63,970)	(415,044)
Transfers out of Level III	129,452	110,965
Consolidations of VIEs		(430,653)
Deconsolidations of VIEs	9,166	7,269
Balance at the end of the period	(2,161,295)	(3,038,534)
Amount of total (losses) gains included in earnings attributable to assets still held at period end	384,981	236,123
Loans held-for-sale \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	63,279	203,865
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	10,593	6,891
Purchases / Originations	445,887	200,570
Sales	(179,296)	(256,964)
Cash repayments / receipts	(197)	(137)
Balance at the end of the period	340,266	154,225
Amount of total (losses) gains included in earnings attributable to assets still held at period end	(6)	2,162
RMBS \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	253,915	176,224
Total realized and unrealized gains (losses):
Included in earnings: Net accretion	3,886	3,415
Included in OCI	1,846	(3,400)
Purchases / Originations		41,470
Cash repayments / receipts	(10,228)	(6,811)
Balance at the end of the period	249,419	210,898
Amount of total (losses) gains included in earnings attributable to assets still held at period end	3,795	3,415
CMBS \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	31,546	212,981
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	(1,343)	967
Purchases / Originations		33,173
Sales	(10,434)
Cash repayments / receipts	(5,766)	(12,303)
Consolidations of VIEs		(138,342)
Deconsolidations of VIEs	1,469	248
Balance at the end of the period	15,472	96,724
Amount of total (losses) gains included in earnings attributable to assets still held at period end	248	1,499
Domestic servicing rights \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	55,082	119,698
Impact of ASU 2015-02 Adoption		(17,467)
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	(8,433)	(6,739)
Balance at the end of the period	46,649	95,492
Amount of total (losses) gains included in earnings attributable to assets still held at period end	(8,433)	(6,739)
VIE Assets \| Level III
Changes in financial assets classified as Level III
Balance at the beginning of the period	67,123,261	76,675,689
Impact of ASU 2015-02 Adoption		17,467
Total realized and unrealized gains (losses):
Included in earnings: Change in fair value / gain on sale	(6,537,225)	(4,089,501)
Consolidations of VIEs	1,127,952	15,103,275
Deconsolidations of VIEs	(1,528,137)	(2,591,268)
Balance at the end of the period	60,185,851	85,115,662
Amount of total (losses) gains included in earnings attributable to assets still held at period end	$ (6,537,225)	$ (4,089,501)

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Amount of adjustment for adoption of accounting pronouncement recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Represents the change due to the consolidations of Variable Interest Entity (VIE) that have taken place during the period in relation to the assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Represents the change due to the deconsolidations of Variable Interest Entity (VIE) that have taken place during the period in relation to the assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets) in change in fair value; the fair value of which assets was or is measured on a recurring basis using significant unobservable inputs (Level 3).

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Amount of gain (loss) recognized on the income statement for a financial instrument classified as an asset measured using unobservable inputs, still held at the end of the period.

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The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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