Variable Interest Entities - Carrying Amounts and Classification of Significant Variable Interests (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 2,521,319	$ 1,503,257
Non-marketable and other securities	625,178	674,946
Accrued interest receivable and other assets	683,180	709,707
Total assets	43,274,037	44,686,703
Total liabilities	39,550,720	41,353,472
Maximum exposure to loss in unconsolidated VIEs	312,693	364,450
Consolidated
Variable Interest Entity [Line Items]
Cash and cash equivalents	12,870	11,811
Non-marketable and other securities	195,956	203,714
Accrued interest receivable and other assets	333	494
Total assets	209,159	216,019
Accrued expenses and other liabilities	909	433
Total liabilities	909	433
Maximum exposure to loss in unconsolidated VIEs	208,300
Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	312,693	364,450
Total assets	312,693	364,450
Accrued expenses and other liabilities	52,846	90,978
Total liabilities	52,846	90,978
Low income housing tax credit funds | Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	106,500	154,400
Unfunded commitments
Variable Interest Entity [Line Items]
Accrued expenses and other liabilities	52,846	90,978
Unfunded commitments | Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	$ 52,800	$ 91,000