Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Details) $ in Thousands	Dec. 31, 2017 USD ($)
OTC Derivative Assets
0-12 Months	$ 174,453
1-5 Years	206,381
Greater Than 5 Years	93,529
Cross- Maturity Netting	(153,610)
Total	320,753
Cross product counterparty netting	(23,732)
Total	297,021
OTC Derivative Liabilities
0-12 Months	148,570
1-5 Years	318,685
Greater Than 5 Years	159,357
Cross-Maturity Netting	(153,610)
Total	473,002
Cross product counterparty netting	(23,732)
Total OTC derivative liabilities included in Trading liabilities	449,270
Exchange traded derivative assets and other credit agreements	28,400
Cash collateral received	146,000
Exchange traded derivative liabilities and other credit agreements	124,100
Cash collateral pledged	318,000
Commodity swaps, options and forwards
OTC Derivative Assets
0-12 Months	0
1-5 Years	4
Greater Than 5 Years	0
Cross- Maturity Netting	(4)
Total	0
OTC Derivative Liabilities
0-12 Months	2,772
1-5 Years	301
Greater Than 5 Years	0
Cross-Maturity Netting	(4)
Total	3,069
Equity swaps and options
OTC Derivative Assets
0-12 Months	3,082
1-5 Years	7,053
Greater Than 5 Years	2,137
Cross- Maturity Netting	(1,442)
Total	10,830
OTC Derivative Liabilities
0-12 Months	78
1-5 Years	172,670
Greater Than 5 Years	3,780
Cross-Maturity Netting	(1,442)
Total	175,086
Credit default swaps
OTC Derivative Assets
0-12 Months	567
1-5 Years	105
Greater Than 5 Years	17,344
Cross- Maturity Netting	(5,625)
Total	12,391
OTC Derivative Liabilities
0-12 Months	104
1-5 Years	16,540
Greater Than 5 Years	3,953
Cross-Maturity Netting	(5,625)
Total	14,972
Total return swaps
OTC Derivative Assets
0-12 Months	34,228
1-5 Years	1,581
Greater Than 5 Years	0
Cross- Maturity Netting	(193)
Total	35,616
OTC Derivative Liabilities
0-12 Months	28,920
1-5 Years	1,517
Greater Than 5 Years	0
Cross-Maturity Netting	(193)
Total	30,244
Foreign currency forwards, swaps and options
OTC Derivative Assets
0-12 Months	108,465
1-5 Years	31,235
Greater Than 5 Years	0
Cross- Maturity Netting	(62,812)
Total	76,888
OTC Derivative Liabilities
0-12 Months	91,640
1-5 Years	31,173
Greater Than 5 Years	0
Cross-Maturity Netting	(62,812)
Total	60,001
Fixed income forwards
OTC Derivative Liabilities
0-12 Months	8,512
1-5 Years	0
Greater Than 5 Years	0
Cross-Maturity Netting	0
Total	8,512
Interest rate swaps, options and forwards
OTC Derivative Assets
0-12 Months	28,111
1-5 Years	166,403
Greater Than 5 Years	74,048
Cross- Maturity Netting	(83,534)
Total	185,028
OTC Derivative Liabilities
0-12 Months	16,544
1-5 Years	96,484
Greater Than 5 Years	151,624
Cross-Maturity Netting	(83,534)
Total	$ 181,118