Variable Interest Entities - Carrying Amounts and Classification of Significant Variable Interests (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 1,854,457	$ 1,503,257
Non-marketable and other securities	664,054	674,946
Accrued interest receivable and other assets	655,543	709,707
Total assets	43,132,654	44,686,703
Total liabilities	39,498,861	41,353,472
Maximum exposure to loss in unconsolidated VIEs	355,134	364,450
Consolidated
Variable Interest Entity [Line Items]
Cash and cash equivalents	8,319	11,811
Non-marketable and other securities	195,482	203,714
Accrued interest receivable and other assets	568	494
Total assets	204,369	216,019
Accrued expenses and other liabilities	894	433
Total liabilities	894	433
Maximum exposure to loss in unconsolidated VIEs	203,500
Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	355,134	364,450
Total assets	355,134	364,450
Accrued expenses and other liabilities	72,231	90,978
Total liabilities	72,231	90,978
Low income housing tax credit funds | Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	153,800	154,400
Unfunded commitments
Variable Interest Entity [Line Items]
Accrued expenses and other liabilities	72,231	90,978
Unfunded commitments | Unconsolidated
Variable Interest Entity [Line Items]
Non-marketable and other securities	$ 72,200	$ 91,000