Regulatory Capital Requirements (Group's and the Bank's actual capital amounts and ratios) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Group [Member]
Capital [Abstract]
Actual - Total capital	$ 860,581	$ 846,748
Actual - Tier 1 capital	801,882	782,912
Actual -Common equity tier 1 capital	612,792	594,482
Actual - Tier 1 leverage capital	801,882	782,912
Minimum Capital - Total Capital	367,907	391,723
Minimum capital - Tier 1 capital	275,930	293,792
Minimum capital - Common equity tier 1 capital	206,948	220,344
Minimum capital - Tier 1 leverage capital	259,711	280,009
Minimum to be well capitalized - Total Capital	459,884	489,654
Minimum to be well capitalized - Tier 1 capital	367,907	391,723
Minimum to be well capitalized - Common equity tier 1 capital	298,924	318,275
Minimum to be well capitalized - Tier 1 leverage	$ 324,639	$ 350,011
Risk Based Ratios [Abstract]
Capital to Risk Weighted Assets	18.71%	17.29%
Tier One Risk Based Capital to Risk Weighted Assets	17.44%	15.99%
Common Equity Tier OneTo Risk Weighted Assets	13.32%	12.14%
Tier One Leverage Capital to Average Assets	12.35%	11.18%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	6.00%	6.00%
Common Equity Tier One Required For Capital Adequacy To Risk Weighted Assets	4.50%	4.50%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets	8.00%	8.00%
Tier One Risk Common Equity Tier One Required To Be Well Capitalized To Risk Weighted Assets	6.50%	6.50%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Bank [Member]
Capital [Abstract]
Actual - Total capital	$ 841,599	$ 815,458
Actual - Tier 1 capital	783,151	751,886
Actual -Common equity tier 1 capital	783,151	751,886
Actual - Tier 1 leverage capital	783,151	751,886
Minimum Capital - Total Capital	367,256	390,688
Minimum capital - Tier 1 capital	275,442	293,016
Minimum capital - Common equity tier 1 capital	206,582	219,762
Minimum capital - Tier 1 leverage capital	258,600	278,399
Minimum to be well capitalized - Total Capital	459,070	488,360
Minimum to be well capitalized - Tier 1 capital	367,256	390,688
Minimum to be well capitalized - Common equity tier 1 capital	298,396	317,434
Minimum to be well capitalized - Tier 1 leverage	$ 323,250	$ 347,999
Risk Based Ratios [Abstract]
Capital to Risk Weighted Assets	18.33%	16.70%
Tier One Risk Based Capital to Risk Weighted Assets	17.06%	15.40%
Common Equity Tier OneTo Risk Weighted Assets	17.06%	15.40%
Tier One Leverage Capital to Average Assets	12.11%	10.80%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	6.00%	6.00%
Common Equity Tier One Required For Capital Adequacy To Risk Weighted Assets	4.50%	4.50%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets	8.00%	8.00%
Tier One Risk Common Equity Tier One Required To Be Well Capitalized To Risk Weighted Assets	6.50%	6.50%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%

The common equity tier 1 capital ratio as defined in the new regulatory framework.

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The amount of Comon Equity Tier 1 required to be categorized as well capitalized under the new regulatory framework.

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The minimum Common Equity Tier One Capital Ratio (Common Equity Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the new regulatory framework.

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Common Equity Tier 1 to Risk Weighted Assets (Common Equity Tier 1 divided by risk weighted assets) as defined by regulations.

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The minimum Common Equity Tier One Capital Ratio (Common Equity Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the new regulatory framework.

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The minimum amount of Common Equity Tier 1 required for capital adequacy purposes under the new regulatory framework.

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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