Variable Interest Entities - Carrying Amounts and Classification of Significant Variable Interests (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 2,619,384	$ 2,923,075	$ 3,795,679	$ 2,545,750
Non-marketable and other equity securities	824,936	651,053
Amortization Method Qualified Affordable Housing Project Investments	225,823	174,214
Accrued interest receivable and other assets	986,523	876,246
Total assets	53,500,787	51,214,467
Total liabilities	48,941,063	46,895,052
Maximum exposure to loss in unconsolidated VIEs	501,810	346,097
Qualified Affordable Housing Project Investments, Commitment	137,783	100,891
Consolidated
Variable Interest Entity [Line Items]
Cash and cash equivalents	5,040	6,674
Non-marketable and other equity securities	200,246	190,562
Accrued interest receivable and other assets	466	365
Total assets	205,752	197,601
Total liabilities	717	990
Maximum exposure to loss in unconsolidated VIEs	205,000
Accrued Liabilities and Other Liabilities	717	990
Unconsolidated
Variable Interest Entity [Line Items]
Cash and cash equivalents	0	0
Non-marketable and other equity securities	501,810	346,097
Accrued interest receivable and other assets	0	0
Total assets	501,810	346,097
Total liabilities	$ 137,783	100,891
Accrued Liabilities and Other Liabilities		$ 100,891