Investment Securities (Marketable Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	$ 1,776,148	$ 1,731,292
Available-for-sale securities, Gross unrealized gains	6,929	14,766
Available-for-sale securities, Gross unrealized losses	(58,410)	(29,670)
Available-for-sale Securities	1,724,667	1,716,388
Held-to-maturity securities	635,705	884,826
Held-to-maturity securities, Gross unrealized gains	654	871
Held-to-maturity securities, Gross unrealized losses	(28,757)	(7,586)
Held-to-maturity securities, fair value	607,602	878,111
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	142,741	312,282
Available-for-sale securities, Gross unrealized gains	1	0
Available-for-sale securities, Gross unrealized losses	(759)	(5,553)
Available-for-sale Securities	141,983	306,729
US Government agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	189,540	70,313
Available-for-sale securities, Gross unrealized gains	47	198
Available-for-sale securities, Gross unrealized losses	(435)	(275)
Available-for-sale Securities	189,152	70,236
Held-to-maturity securities	433,343	687,302
Held-to-maturity securities, Gross unrealized gains	7	4
Held-to-maturity securities, Gross unrealized losses	(24,470)	(7,144)
Held-to-maturity securities, fair value	408,880	680,162
Municipal
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	129,446	105,702
Available-for-sale securities, Gross unrealized gains	2,969	3,249
Available-for-sale securities, Gross unrealized losses	(606)	(356)
Available-for-sale Securities	131,809	108,595
Held-to-maturity securities	202,362	197,524
Held-to-maturity securities, Gross unrealized gains	647	867
Held-to-maturity securities, Gross unrealized losses	(4,287)	(442)
Held-to-maturity securities, fair value	198,722	197,949
Corporate notes, financial issuers
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	65,260	80,014
Available-for-sale securities, Gross unrealized gains	132	1,510
Available-for-sale securities, Gross unrealized losses	(1,000)	(1,481)
Available-for-sale Securities	64,392	80,043
Corporate notes, other
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	1,000	1,500
Available-for-sale securities, Gross unrealized gains	0	4
Available-for-sale securities, Gross unrealized losses	(1)	(2)
Available-for-sale Securities	999	1,502
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	1,185,448	1,069,680
Available-for-sale securities, Gross unrealized gains	284	3,834
Available-for-sale securities, Gross unrealized losses	(54,330)	(21,004)
Available-for-sale Securities	1,131,402	1,052,510
Mortgage-backed, collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	30,105	40,421
Available-for-sale securities, Gross unrealized gains	67	172
Available-for-sale securities, Gross unrealized losses	(490)	(506)
Available-for-sale Securities	29,682	40,087
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	32,608	51,380
Available-for-sale securities, Gross unrealized gains	3,429	5,799
Available-for-sale securities, Gross unrealized losses	(789)	(493)
Available-for-sale Securities	35,248	$ 56,686
Subprime
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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