Junior Subordinated Debentures (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Average Term of Junior Subordinated Debentures	30 years
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Amount	$ 245,293,000	$ 245,290,000
Interest Expense, Junior Subordinated Debentures	19,600,000
Junior Subordinated Debt [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate	2.55%
Amount	245,293,000
Junior Subordinated Debt [Member] | Sterling Capital Trust IX [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	1.86%
Amount	46,392,000
Junior Subordinated Debt [Member] | Sterling Capital Trust VIII [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	2.02%
Amount	51,547,000
Junior Subordinated Debt [Member] | Sterling Capital Trust VII [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	1.91%
Amount	56,702,000
Junior Subordinated Debt [Member] | Lynnwood Capital Trust II [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	2.19%
Amount	10,310,000
Junior Subordinated Debt [Member] | Sterling Capital Trust VI [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	3.59%
Amount	10,310,000
Junior Subordinated Debt [Member] | Sterling Capital Statutory Trust V [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	3.62%
Amount	20,619,000
Junior Subordinated Debt [Member] | Sterling Capital Trust IV [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	3.58%
Amount	10,310,000
Junior Subordinated Debt [Member] | Sterling Capital Trust III [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	3.69%
Amount	14,433,000
Junior Subordinated Debt [Member] | Lynnwood Capital Trust I [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	3.52%
Amount	9,440,000
Junior Subordinated Debt [Member] | Klamath First Capital Trust I [Member]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Abstract]
Rate at June 30, 2012	4.48%
Amount	$ 15,230,000