Shareholders' Equity (Capital) (Details 1) $ / shares in Units, $ in Thousands	2 Months Ended	12 Months Ended			222 Months Ended
	Feb. 14, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) Y $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders' Equity		$ 1,286,832	$ 1,268,200	$ 1,231,868	$ 1,286,832	$ 1,161,537
Well Capitalized Minimum Common Equity Tier One Ratio (as a percent)		6.50%	6.50%		6.50%
Well Capitalized Minimum Tier 1 Capital Ratio (as a percent)		8.00%	8.00%		8.00%
Well Capitalized Minimum Total Capital Ratio (as a percent)		10.00%	10.00%		10.00%
Well Capitalized Minimum Tier 1 Leverage Ratio (as a percent)		5.00%	5.00%		5.00%
Dividends
Number of prior calendar years considered for payment of dividends in excess of the sum of net income | Y		2
Common Stock Repurchase Program
Number of shares of common stock repurchased | shares		1,642,998			56,900,000
Amount returned to shareholders on stock repurchase		$ 137,649	$ 91,988	$ 47,076	$ 2,300,000
Average cost of shares repurchased (in dollars per share) | $ / shares		$ 81.98			$ 40.38
Treasury Stock Value Acquired Cost Method Share Repurchase Program		$ 134,700
Parent [Member]
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders' Equity		1,286,832	1,268,200		$ 1,286,832
Common Equity Tier One Capital		1,289,424	1,290,723		1,289,424
Tier 1 Capital		1,289,424	1,290,723		1,289,424
Total Capital		$ 1,406,273	$ 1,404,238		$ 1,406,273
Common Equity Tier One Ratio		12.18%	13.07%		12.18%
Tier 1 Capital Ratio (as a percent)		12.18%	13.07%		12.18%
Total Capital Ratio (as a percent)		13.28%	14.21%		13.28%
Tier 1 Leverage Ratio (as a percent)		7.25%	7.60%		7.25%
Subsidiaries [Member]
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders' Equity		$ 1,229,775	$ 1,195,132		$ 1,229,775
Common Equity Tier One Capital		1,243,939	1,229,227		1,243,939
Tier 1 Capital		1,243,939	1,229,227		1,243,939
Total Capital		$ 1,360,788	$ 1,342,742		$ 1,360,788
Common Equity Tier One Ratio		11.76%	12.46%		11.76%
Tier 1 Capital Ratio (as a percent)		11.76%	12.46%		11.76%
Total Capital Ratio (as a percent)		12.87%	13.61%		12.87%
Tier 1 Leverage Ratio (as a percent)		7.01%	7.24%		7.01%
Subsequent Event
Common Stock Repurchase Program
Number of shares of common stock repurchased | shares	114,358
Amount returned to shareholders on stock repurchase	$ 10,600
Average cost of shares repurchased (in dollars per share) | $ / shares	$ 92.63