Fair Value Measurements (Details) (USD $)	3 Months Ended																																																																																3 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Impaired Loans [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Impaired Loans [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Covered Real Estate Owned [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Covered Real Estate Owned [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Real Estate Held for Sale [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value Total [Member] Real Estate Held for Sale [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 1 [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 1 [Member] Impaired Loans [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 1 [Member] Covered Real Estate Owned [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 1 [Member] Real Estate Held for Sale [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member] Impaired Loans [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member] Covered Real Estate Owned [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member] Real Estate Held for Sale [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Impaired Loans [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Impaired Loans [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Covered Real Estate Owned [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Covered Real Estate Owned [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Real Estate Held for Sale [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member] Real Estate Held for Sale [Member]	Dec. 31, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Equity Securities [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 US Treasury and Government [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Obligations of States and Political Subdivisions [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Obligations of foreign governments [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Obligations of foreign governments [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Obligations of foreign governments [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Obligations of foreign governments [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Corporate Debt Securities [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Collateralized Mortgage Backed Securities [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Sep. 30, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Fair Value Total [Member]	Dec. 31, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Sep. 30, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 1 [Member]	Dec. 31, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Sep. 30, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 2 [Member]	Dec. 31, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Sep. 30, 2013 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Fair Value, Measurements, Recurring [Member] Level 3 [Member]	Dec. 31, 2013 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2013 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Impaired Loans [Member]	Dec. 31, 2012 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Impaired Loans [Member]	Dec. 31, 2013 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Covered Real Estate Owned [Member]	Dec. 31, 2012 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Covered Real Estate Owned [Member]	Dec. 31, 2013 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Real Estate Held for Sale [Member]	Dec. 31, 2012 Change During Period, Fair Value Disclosure [Member] Fair Value, Measurements, Nonrecurring [Member] Real Estate Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		$ 2,838,504,000	$ 2,360,948,000	$ 2,838,504,000	$ 2,360,948,000	$ 100,246,000	$ 100,726,000	$ 2,738,258,000	$ 2,260,222,000	$ 0	$ 0																									$ 100,749,000	$ 101,237,000	$ 100,246,000	$ 100,726,000	$ 503,000	$ 511,000	$ 0	$ 0	$ 631,326,000	$ 533,975,000	$ 0	$ 0	$ 631,326,000	$ 533,975,000	$ 0	$ 0	$ 22,640,000	$ 22,545,000	$ 0	$ 0	$ 22,640,000	$ 22,545,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 450,113,000	$ 452,015,000	$ 0	$ 0	$ 450,113,000	$ 452,015,000	$ 0	$ 0	$ 0	$ 1,633,676,000	$ 1,251,176,000	$ 0	$ 0	$ 1,633,676,000	$ 1,251,176,000	$ 0	$ 0
Assets												17,208,000	49,744,000	5,580,000	21,238,000	1,286,000	3,080,000	10,342,000	25,426,000	0	0	0	0	0	0	0	0	17,208,000	49,744,000	5,580,000	21,238,000	1,286,000	3,080,000	10,342,000	25,426,000
Loss Related to Impaired Loans and Real Estate Held for Sale, Measured on Nonrecurring Basis																																																																																	2,985,000	17,440,000	(805,000)	9,813,000	65,000	91,000	3,725,000	7,536,000
Liabilities, Fair Value Disclosure, Recurring		0
Liabilities, Fair Value Disclosure, Nonrecurring		0
Gain on sale of investments	$ 0