Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended			12 Months Ended												3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2013	Mar. 15, 2013	Dec. 15, 2012	Sep. 30, 2012	Jan. 15, 2012	Dec. 31, 2013 The Commerce Bank Of Oregon [Member]	Dec. 31, 2013 Maximum [Member] The Commerce Bank Of Oregon [Member]	Dec. 31, 2013 Minimum [Member] The Commerce Bank Of Oregon [Member]	Mar. 31, 2012 Director [Member]	Dec. 31, 2013 Director [Member]	Dec. 31, 2012 Director [Member]	Dec. 31, 2011 Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock expected to vest	400,124			400,124
Restricted Stock Units expected to vest	1,146,807			1,146,807
Share Based Compensation Restricted Stock Awards Aggregate Intrinsic Value	$ 12.0			$ 12.0
Share Based Compensation Restricted Stock Units Aggregate Intrinsic Value	34.4			34.4
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price	$ 24.38			$ 24.38
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	5 years 9 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	9.7			9.7
Restricted Stock Units Outstanding	1,522,038	822,753	146,165	1,522,038	822,753	146,165	0
Weighted Average Grant Price of Restricted Stock Forfeited				$ 20.13	$ 20.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 35.54	$ 38.87	$ 43.06	$ 35.54	$ 38.87	$ 43.06	$ 47.37							$ 20.58	$ 17.85
Common stock, outstanding shares	184,677,696	184,199,198		184,677,696	184,199,198								1,038,000
Stock Options without a fixed expiration date	21,250			21,250
Granted Salary Share Units - Share Settled					456,275
Total shares authorized under stock option and incentive plan	19,500,000			19,500,000
Number of shares available for future grants of stock options or restricted stock	5,696,668			5,696,668
Compensation expense not yet recognized for nonvested share-based awards	25.2			25.2
Nonvested share-based awards, expected weighted average period to be recognized, years	2 years 4 months 24 days
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options				0.3	2.8	2.8
Total intrinsic value of stock options exercised				4.0	0.7	0.4
Cash received from the exercise of stock options				9.8	1.9	0.6
Aggregate intrinsic value of outstanding stock options	23.6	5.4		23.6	5.4
Aggregate intrinsic value of exercisable options	13.7	3.2		13.7	3.2
Outstanding stock options, Weighted average remaining contractual life (years)	2 years 1 month 6 days	2 years 7 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	1,729,543			1,729,543
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	5,874,590	5,962,325	5,933,870	5,874,590	5,962,325	5,933,870	6,369,239						44,100
Total fair value of restricted stock vesting				13.1	15.5	17.6
Weighted average issue price	$ 24.55	$ 17.57	$ 23.43
Total fair value granted				13.1	15.5	17.6
Granted Salary Share Units Cash Settled						297,620
Settled Salary Share Units - Cash Settled								231,061		125,070	225,214	172,550
Cash Paid for Salary Share Units									$ 5.7	$ 2.7	$ 4.5	$ 3.2
Stock Issued During Period, Shares, Restricted Stock Award, Gross				56,774	87,480	616,234											17,444	25,536	26,433
Restricted Stock Units Granted				949,418	726,779		146,165									7,296	4,984
Weighted Average Grant Price of Restricted Stock Units Granted				$ 25.99	$ 18.29	$ 23.69
Restricted Stock Units Vested				(160,580)	(34,885)
Weighted Average Grant Price of Restricted Stock Units Vested				$ 20.17	$ 22.46