Securities (Tables)

12 Months Ended

Dec. 31, 2014

Available-for-sale Securities [Abstract]

Securities Available for Sale

The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of securities available for sale:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
December 31, 2014	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,160,378	$	10,219	$	(8,210	)	$	1,162,387
State and municipal securities	483,578		14,432		(1,526		)	496,484
U.S. government agency and government-sponsored enterprise securities	416,919		856		(4,069		)	413,706
U.S. government securities	20,910		—		(411		)	20,499
Other securities	5,284		20		(123		)	5,181
Total	$	2,087,069	$	25,527	$	(14,339	)	$	2,098,257
December 31, 2013
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	961,442	$	10,640	$	(23,674	)	$	948,408
State and municipal securities	357,013		11,450		(3,993		)	364,470
U.S. government agency and government-sponsored enterprise securities	335,671		434		(10,066		)	326,039
U.S. government securities	21,081		—		(967		)	20,114
Other securities	5,284		27		(231		)	5,080
Total	$	1,680,491	$	22,551	$	(38,931	)	$	1,664,111

Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table Text Block]

The following table provides the gross realized gains and losses on the sales and calls of securities for the periods indicated:

	Years Ended December 31,
	2014			2013			2012
	(in thousands)
Gross realized gains	$	553		$	632		$	4,447
Gross realized losses	(1		)	(170		)	(714		)
Net realized gains	$	552		$	462		$	3,733

Schedule of Contractual Maturities of Investment Securities Available for Sale

The scheduled contractual maturities of investment securities available for sale at December 31, 2014 are presented as follows:

	December 31, 2014
	Amortized Cost		Fair Value
	(in thousands)
Due within one year	$	18,872	$	19,028
Due after one year through five years	426,532		426,035
Due after five years through ten years	534,515		537,175
Due after ten years	1,101,866		1,110,838
Other securities with no stated maturity	5,284		5,181
Total investment securities available-for-sale	$	2,087,069	$	2,098,257

Schedule of Securities pledged as collateral [Table Text Block]

The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:

	December 31, 2014		December 31, 2013
	(in thousands)
Washington and Oregon State to secure public deposits	$	328,400	$	277,012
Federal Reserve Bank to secure borrowings	41,146		42,694
Other securities pledged	157,097		43,081
Total securities pledged as collateral	$	526,643	$	362,787

Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses

The following tables show the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2014 and 2013:

	Less than 12 Months					12 Months or More					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2014	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	258,825	$	(1,287	)	$	279,015	$	(6,924	)	$	537,840	(8,211		)
State and municipal securities	71,026		(543		)	44,148		(982		)	115,174		(1,525		)
U.S. government agency and government-sponsored enterprise securities	105,250		(518		)	216,221		(3,551		)	321,471		(4,069		)
U.S. government securities	—		—			19,450		(411		)	19,450		(411		)
Other securities	2,313		(2		)	2,834		(121		)	5,147		(123		)
Total	$	437,414	$	(2,350	)	$	561,668	$	(11,989	)	$	999,082	$	(14,339	)
December 31, 2013
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	492,921	$	(10,991	)	$	121,303	$	(12,684	)	$	614,224	$	(23,675	)
State and municipal securities	112,400		(3,069		)	13,815		(923		)	126,215		(3,992		)
U.S. government agency and government-sponsored enterprise securities	260,001		(8,063		)	28,447		(2,003		)	288,448		(10,066		)
U.S. government securities	20,114		(967		)	—		—			20,114		(967		)
Other securities	2,257		(58		)	2,783		(173		)	5,040		(231		)
Total	$	887,693	$	(23,148	)	$	166,348	$	(15,783	)	$	1,054,041	$	(38,931	)