Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Jan. 01, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		$ 568,356	$ 694,535
Operating income		69,506	89,214
Income taxes		19,979	25,721
Net income for common stock		31,866	45,787
Other		481,531		$ 542,523
Liabilities and Equity		11,273,447		11,185,142
Liabilities		9,341,245		9,360,276
Retained earnings		296,680		296,654
Common stock equity		1,897,909	1,745,124	1,790,573		$ 1,726,406
Net income	[1]	32,339	46,260
Increase in deferred income taxes	[1]	3,828	6,457
Change in other assets and liabilities	[1]	(25,992)	(29,931)
American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 700
Amortization Method Qualified Affordable Housing Project Investments, Amortization		1,300
Affordable Housing Tax Credit, Amount		1,400
Affordable Housing Tax Credit, Other Tax Benefits, Amount		500
Income taxes		7,156	8,133
Other		305,917		305,416
Liabilities		5,181,271		5,032,434
Retained earnings		217,909		211,934
Common stock equity		543,606		533,788
Net income		13,475	14,399
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			24,673
Net income for common stock			45,927
Other				541,542
Liabilities and Equity				11,184,161
Deferred Income Tax Liabilities And Other Liabilities				631,734
Liabilities				9,358,440
Retained earnings				297,509		255,694
Common stock equity				1,791,428		1,727,070
Net income			46,400
Increase in deferred income taxes		15,265	6,298
Change in other assets and liabilities		19,826	(27,208)
Scenario, Previously Reported | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			7,085
Net income for common stock			14,539
Other				304,435
Liabilities and Equity				5,565,241
Deferred Income Tax Liabilities And Other Liabilities				116,527
Liabilities				5,030,598
Retained earnings				212,789
Common stock equity				534,643
Restatement Adjustment | Capital Expenditure Accruals
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in other assets and liabilities			(2,704)
Accounting Standards Update 2014-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			25,721
Net income for common stock			45,787
Other				542,523
Liabilities and Equity				11,185,142
Deferred Income Tax Liabilities And Other Liabilities				633,570
Liabilities				9,360,276
Retained earnings				296,654		255,030
Common stock equity				1,790,573		1,726,406
Net income			46,260
Increase in deferred income taxes			6,457
Change in other assets and liabilities			(29,931)
Accounting Standards Update 2014-01 | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			8,133
Net income for common stock			14,399
Other				305,416
Liabilities and Equity				5,566,222
Deferred Income Tax Liabilities And Other Liabilities				118,363
Liabilities				5,032,434
Retained earnings				211,934
Common stock equity				533,788
Accounting Standards Update 2014-01 | Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in other assets and liabilities			(27,227)
Accounting Standards Update 2014-01 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			1,048
Net income for common stock			(140)
Other				981
Liabilities and Equity				981
Deferred Income Tax Liabilities And Other Liabilities				1,836
Liabilities				1,836
Retained earnings				(855)		(664)
Common stock equity				(855)		$ (664)
Net income			(140)
Increase in deferred income taxes			159
Change in other assets and liabilities			(19)
Accounting Standards Update 2014-01 | Restatement Adjustment | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes			1,048
Net income for common stock			(140)
Other				981
Liabilities and Equity				981
Deferred Income Tax Liabilities And Other Liabilities				1,836
Liabilities				1,836
Retained earnings				(855)
Common stock equity				(855)
Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		43,717	41,088
Operating income		20,631	22,531
Income taxes		7,156	8,133
Net income for common stock		13,475	14,399
Net income		13,475	14,399
Bank | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liabilities and Equity		$ 5,724,877		$ 5,566,222
Bank | Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			41,996
Operating income			21,623
Bank | Scenario, Previously Reported | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			38,370
Operating income			21,624
Bank | Accounting Standards Update 2014-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			41,088
Operating income			22,531
Bank | Accounting Standards Update 2014-01 | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			37,462
Operating income			22,532
Bank | Accounting Standards Update 2014-01 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			(908)
Operating income			908
Bank | Accounting Standards Update 2014-01 | Restatement Adjustment | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses			(908)
Operating income			$ 908

[1] As restated - See Note 1, “Basis of presentation - Restatement of previously issued financial statements.”