Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Regulatory Capital [Abstract]
Common Equity Tier One Capital	$ 2,084,589
Common Equity Tier One Capital to Risk Weighted Assets	10.50%
Common Equity Tier One Capital Required for Capital Adequacy	$ 893,289
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Parent Company [Member]
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,515,861	$ 2,350,898
Total Capital Actual Ratio	12.62%	12.66%
Total Capital for Capital Adequacy Purposes Amount	$ 1,594,397	$ 1,485,412
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 Capital Actual Amount	$ 2,016,861	$ 1,868,059
Tier 1 Capital Actual Ratio	10.12%	10.06%
Tier 1 Capital for Adequacy Purposes Amount	$ 797,199	$ 742,706
Tier 1 Capital for Adequacy Purposes Ratio	4.00%	4.00%
Common Equity Tier One Capital	$ 1,897,944
Common Equity Tier One Capital to Risk Weighted Assets	9.52%
Common Equity Tier One Capital Required for Capital Adequacy	$ 896,848
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Tier 1 Leverage Capital Actual Amount	$ 2,016,861	$ 1,868,059
Tier 1 Leverage Capital Actual Ratio	7.60%	7.48%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,061,325	$ 998,967
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Subsidiaries [Member]
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,532,563	$ 2,449,514
Total Capital Actual Ratio	12.76%	13.26%
Total Capital for Capital Adequacy Purposes Amount	$ 1,588,070	$ 1,477,785
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Total Capital to be Well Capitalized Amount	$ 1,985,088	$ 1,847,231
Total Capital to be Well Capitalized Ratio	10.00%	10.00%
Tier 1 Capital Actual Amount	$ 2,283,785	$ 2,217,861
Tier 1 Capital Actual Ratio	11.50%	12.01%
Tier 1 Capital for Adequacy Purposes Amount	$ 794,035	$ 738,892
Tier 1 Capital for Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 Capital To Be Well Capitalized Amount	$ 1,191,053	$ 1,108,339
Tier 1 Capital To Be Well Capitalized Ratio	6.00%	6.00%
Tier 1 Equity Capital to be Well Capitalized Amount	$ 1,290,307
Tier 1 Equity Capital to be Well Capitalized Ratio	6.50%
Tier 1 Leverage Capital Actual Amount	$ 2,283,785	$ 2,217,861
Tier 1 Leverage Capital Actual Ratio	8.64%	8.92%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,057,228	$ 994,103
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 Leverage Capital To Be Well Capitalized Amount	$ 1,321,535	$ 1,242,628
Tier 1 Leverage Capital To Be Well Capitalized Ratio	5.00%	5.00%