Investment (Held-to-Maturity) Securities (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Mar. 31, 2016 USD ($)
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 519,402		$ 546,145		$ 576,004
Investments Securities, Carrying Value		519,402		546,145		576,047
Investment Securities, fair value		540,663		565,493		609,743
Investment Securities, Gross Unrealized Gain		22,713	[1]	21,154	[2]	33,828	[3]
Investment Securities, Gross Unrealized Loss		(1,452)	[1]	(1,806)	[2]	(132)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Carrying Value		519,402		546,145		576,047
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 540,663		565,493		609,743
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		3.64%
Investment Securities, Pledged as Collateral [Abstract]
Investment Securities, Pledged as Collateral, Carrying Value		$ 290,417		322,208		263,720
Investment Securities, Pledged as Collateral, Fair Value		$ 293,352		$ 323,808		$ 268,422
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		146		193		26
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 145,869		$ 236,070		$ 14,175
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		1,563		5,188		6,240
Investment Securities, Continuous Unrealized Loss Position, Fair Value		147,432		241,258		20,415
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,412		1,709		8
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		40		97		124
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		1,452		1,806		132
Fixed Maturity Securities [Member]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		104,243
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		196,878
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		138,188
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		60,715
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		500,024
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		104,552
Investment Securities, Debt Maturities, One to Five Years, Fair Value		200,546
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		153,991
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		61,607
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		$ 520,696
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		1.91%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		2.81%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.71%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.88%
Investment Securities, Debt Maturities, Nominal Yield		3.68%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	4.80
Municipal and other tax-exempt securities
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 298,811		320,364		347,684
Investments Securities, Carrying Value		298,811		320,364		347,684
Investment Securities, fair value		301,128		321,225		352,542
Investment Securities, Gross Unrealized Gain		2,872	[1]	2,272	[2]	4,952	[3]
Investment Securities, Gross Unrealized Loss		(555)	[1]	(1,411)	[2]	(94)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		89,707
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		151,490
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		12,314
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		45,300
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		298,811
Investments Securities, Debt Maturities, Carrying Value		298,811		320,364		347,684
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		89,749
Investment Securities, Debt Maturities, One to Five Years, Fair Value		151,869
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		12,699
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		46,811
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		301,128
Investment Securities, Debt Maturities, Fair Value		$ 301,128		$ 321,225		$ 352,542
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	[5]	1.62%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	[5]	2.16%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	[5]	4.73%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	[5]	5.02%
Investment Securities, Debt Maturities, Nominal Yield	[5]	2.54%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	3.49
Investment Securities,Debt Maturities, Effective tax rate for nominal yield calculation		39.00%
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		102		151		19
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 127,374		$ 219,892		$ 14,175
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		1,563		4,333		4,364
Investment Securities, Continuous Unrealized Loss Position, Fair Value		128,937		224,225		18,539
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		515		1,316		8
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		40		95		86
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		555		1,411		94
Other debt securities
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		201,213		205,004		202,997
Investments Securities, Carrying Value		201,213		205,004		202,997
Investment Securities, fair value		219,568		222,795		230,407
Investment Securities, Gross Unrealized Gain		19,172	[1]	18,115	[2]	27,448	[3]
Investment Securities, Gross Unrealized Loss		(817)	[1]	(324)	[2]	(38)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		14,536
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		45,388
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		125,874
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		15,415
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		201,213
Investments Securities, Debt Maturities, Carrying Value		201,213		205,004		202,997
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		14,803
Investment Securities, Debt Maturities, One to Five Years, Fair Value		48,677
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		141,292
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		14,796
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		219,568
Investment Securities, Debt Maturities, Fair Value		$ 219,568		$ 222,795		$ 230,407
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		3.74%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.98%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.81%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.46%
Investment Securities, Debt Maturities, Nominal Yield		5.37%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	6.75
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		43		41		7
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 14,440		$ 11,820		$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0		855		1,876
Investment Securities, Continuous Unrealized Loss Position, Fair Value		14,440		12,675		1,876
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		817		322		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		2		38
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		817		324		38
U.S. government agency residential mortgage-backed securities
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Net Carrying Value		19,378
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Fair Value		$ 19,967
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	[6]	2.76%
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities		4 years 219 days
U.S. government agency residential mortgage-backed securities | Other [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 19,378		20,777		25,323
Investments Securities, Carrying Value		19,378		20,777		25,366
Investment Securities, fair value		19,967		21,473		26,794
Investment Securities, Gross Unrealized Gain		669	[1]	767	[2]	1,428	[3]
Investment Securities, Gross Unrealized Loss		(80)	[1]	(71)	[2]	0	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Carrying Value		19,378		20,777		25,366
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 19,967		$ 21,473		$ 26,794
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1		1		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 4,055		$ 4,358		$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value		4,055		4,358		0
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		80		71		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 80		$ 71		$ 0

[1] Gross unrealized gains and losses are not recognized in Accumulated Other Comprehensive Income "AOCI" in the Consolidated Balance Sheets.

[2] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[3] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[4] Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty.

[5] Calculated on a taxable equivalent basis using a 39 percent effective tax rate.

[6] The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio.