Investment Securities (Available-for-sale Securities with Unrealized Loss) (Details) $ in Thousands	Mar. 31, 2016 USD ($) securities	Dec. 31, 2015 USD ($) securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 71,151	$ 320,460
Less than 12 months, unrealized loss	$ 580	$ 4,018
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities	19	90
12 months or more, fair value	$ 118,790	$ 104,915
12 months or more, unrealized loss	$ 2,771	$ 4,781
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	41	38
Total unrealized loss position, fair value	$ 189,941	$ 425,375
Total unrealized loss	3,351	8,799
States and political subdivisions
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	0	7,662
Less than 12 months, unrealized loss	$ 0	$ 38
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities	0	8
12 months or more, fair value	$ 215	$ 213
12 months or more, unrealized loss	$ 3	$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	1	1
Total unrealized loss position, fair value	$ 215	$ 7,875
Total unrealized loss	3	44
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	69,140	303,549
Less than 12 months, unrealized loss	$ 415	$ 3,902
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities	17	76
12 months or more, fair value	$ 116,130	$ 102,090
12 months or more, unrealized loss	$ 2,039	$ 4,214
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	36	33
Total unrealized loss position, fair value	$ 185,270	$ 405,639
Total unrealized loss	2,454	8,116
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value		6,682
Less than 12 months, unrealized loss		$ 44
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities		3
12 months or more, fair value		$ 0
12 months or more, unrealized loss		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities		0
Total unrealized loss position, fair value		$ 6,682
Total unrealized loss		44
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	1,991	2,129
Less than 12 months, unrealized loss	$ 163	$ 19
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities	1	1
12 months or more, fair value	$ 2,339	$ 2,506
12 months or more, unrealized loss	$ 659	$ 492
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	3	3
Total unrealized loss position, fair value	$ 4,330	$ 4,635
Total unrealized loss	$ 822	511
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	3
Equity securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 20	438
Less than 12 months, unrealized loss	$ 2	$ 15
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | securities	1	2
12 months or more, fair value	$ 106	$ 106
12 months or more, unrealized loss	$ 70	$ 69
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	1	1
Total unrealized loss position, fair value	$ 126	$ 544
Total unrealized loss	$ 72	$ 84
Mortgage-backed securities, issued by US government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	97.00%
Mortgage-backed securities, privately issued
Available-for-sale securities that had an unrealized loss:
Less than 12 months, no. of securities | securities	3
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	3.00%
Number of privately issued mortgage-backed securities securities with book value less than 90% of fair value | securities	2
Fair value within book value	100.00%
Fair Value Less Than 90 Percent of Book Value [Member] | Mortgage-backed securities, privately issued
Available-for-sale securities that had an unrealized loss:
12 months or more, fair value	$ 500
Book value of privately issued mortgage-backed securities in unrealized loss position for more than 12 months	$ 700