Securities Available for Sale (Tables)

3 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of amortized cost and fair value of investments

The amortized cost and approximate fair value of investments in securities, all of which are classified as available for sale according to management’s intent, are summarized as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(dollars in thousands)
As of December 31, 2016
U.S. Treasury securities	$	227,265	$	1,417	$	(15	)	$	228,667
Mortgage-backed securities:
Government National Mortgage Association	633,330		485		(8,123		)	625,692
Federal National Mortgage Association	281,741		—		(3,179		)	278,562
Small Business Assistance Program	167,328		283		(1,653		)	165,958
States and political subdivision securities	68,410		2		(1,808		)	66,604
Corporate debt securities	4,998		24		—			5,022
Other	1,013		40		—			1,053
Total	$	1,384,085	$	2,251	$	(14,778	)	$	1,371,558

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(dollars in thousands)
As of September 30, 2016
U.S. Treasury securities	$	227,007	$	3,973	$	—		$	230,980
U.S. Agency securities	—		—		—			—
Mortgage-backed securities:
Government National Mortgage Association	664,529		3,172		(1,922		)	665,779
Federal National Mortgage Association	212,452		1,324		—			213,776
Small Business Assistance Program	142,921		2,362		—			145,283
States and political subdivision securities	55,525		123		(164		)	55,484
Corporate debt securities	4,998		24		—			5,022
Other	1,013		49		—			1,062
Total	$	1,308,445	$	11,027	$	(2,086	)	$	1,317,386

Schedule of amortized cost and fair value of investments by contractual maturity

The amortized cost and approximate fair value of debt securities available for sale as of December 31, 2016 and September 30, 2016, by contractual maturity, are shown below. Maturities of mortgage-backed securities may differ from contractual maturities because the mortgages underlying the securities may be called or repaid without penalty.

	December 31, 2016				September 30, 2016
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(dollars in thousands)
Due in one year or less	$	5,182	$	5,173	$	3,706	$	3,709
Due after one year through five years	274,901		275,386		265,253		269,242
Due after five years through ten years	20,468		19,612		18,449		18,413
Due after ten years	122		122		122		122
	300,673		300,293		287,530		291,486
Mortgage-backed securities	1,082,399		1,070,212		1,019,902		1,024,838
Securities without contractual maturities	1,013		1,053		1,013		1,062
Total	$	1,384,085	$	1,371,558	$	1,308,445	$	1,317,386

Schedule of gross unrealized losses on investments

The following table presents the Company’s gross unrealized losses and approximate fair value in investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

						December 31, 2016
	Less than 12 months					12 months or more					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
	(dollars in thousands)
U.S. Treasury securities	$	—	$	—		$	9,463	$	(15	)	$	9,463	$	(15	)
Mortgage-backed securities	320,099		(4,424		)	643,908		(8,531		)	964,007		(12,955		)
States and political subdivision securities	63,813		(1,808		)	—		—			63,813		(1,808		)
Total	$	383,912	$	(6,232	)	$	653,371	$	(8,546	)	$	1,037,283	$	(14,778	)

						September 30, 2016
	Less than 12 months					12 months or more					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
	(dollars in thousands)
U.S. Treasury securities	$	—	$	—		$	—	$	—		$	—	$	—
Mortgage-backed securities	$	17,528	$	(6	)	$	284,995	$	(1,916	)	$	302,523	$	(1,922	)
States and political subdivision securities	27,933		(164		)	—		—			27,933		(164		)
Total	$	45,461	$	(170	)	$	284,995	$	(1,916	)	$	330,456	$	(2,086	)

Schedule of net unrealized gains (losses) on securities

The components of accumulated other comprehensive income (loss) from net unrealized gains (losses) on securities available for sale for the three months ended December 31, 2016 and 2015, are as follows:

	Three Months Ended December 31,
	2016			2015
	(dollars in thousands)
Beginning balance accumulated other comprehensive income	$	5,534		$	2,318
Net unrealized holding (loss) arising during the period	(21,468		)	(11,915		)
Reclassification adjustment for net gain (loss) realized in net income	—			(354		)
Net change in unrealized (loss) before income taxes	(21,468		)	(12,269		)
Income tax benefit	8,158			4,662
Net change in unrealized (loss) on securities after taxes	(13,310		)	(7,607		)
Ending balance accumulated other comprehensive (loss)	$	(7,776	)	$	(5,289	)