Securities (Securities in a Continuous Unrealized Loss Position) (Details) $ in Thousands	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	31	47
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 199,567	$ 505,906
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (1,416)	$ (12,726)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	40	10
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 395,580	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (12,119)	$ (3,115)
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	71	57
Fair value of securities in a continuous unrealized loss position total	$ 595,147	$ 532,642
Unrealized losses of securities in a continuous unrealized loss position total	$ (13,535)	$ (15,841)
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	8	10
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 69,681	$ 98,433
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (798)	$ (3,050)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	8	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 87,923	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (3,077)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	16	10
Fair value of securities in a continuous unrealized loss position total	$ 157,604	$ 98,433
Unrealized losses of securities in a continuous unrealized loss position total	$ (3,875)	$ (3,050)
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	20	35
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 128,965	$ 407,073
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (613)	$ (9,671)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	22	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 279,693	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (7,120)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	42	35
Fair value of securities in a continuous unrealized loss position total	$ 408,658	$ 407,073
Unrealized losses of securities in a continuous unrealized loss position total	$ (7,733)	$ (9,671)
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	0	0
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 0	$ 0
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ 0	$ 0
Number of securities in a continuous unrealized loss position for 12 months or longer | security	7	10
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 16,984	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (1,122)	$ (3,115)
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	7	10
Fair value of securities in a continuous unrealized loss position total	$ 16,984	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position total	$ (1,122)	$ (3,115)
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	3	2
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 921	$ 400
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (5)	$ (5)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	3	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 10,980	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (800)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	6	2
Fair value of securities in a continuous unrealized loss position total	$ 11,901	$ 400
Unrealized losses of securities in a continuous unrealized loss position total	$ (805)	$ (5)