Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jan. 01, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses	$ 551,182	$ 715,474	$ 1,119,538	$ 1,410,009
Operating income	72,730	83,183	142,236	172,397
Income taxes	20,911	23,317	40,890	49,038
Net income for common stock	35,018	41,281	66,884	87,068
Other	493,151		493,151		$ 542,523
Liabilities and Equity	11,439,631		11,439,631		11,185,142
Deferred Income Tax Liabilities And Other Liabilities					633,570
Liabilities	9,506,818		9,506,818		9,360,276
Retained earnings	298,398		298,398		296,654		$ 255,030
Common stock equity	1,898,520	1,759,935	1,898,520	1,759,935	1,790,573		1,726,406
American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting principle in period						$ 700
Low income housing tax credits, amortization	1,200		2,500
Low income housing tax credits, tax credits	1,200		2,600
Low income housing tax credits, other tax benefits	500		1,100
Income taxes	6,875	6,420	14,031	14,553
Net income for common stock		11,536		25,935
Other	305,310		305,310		305,416
Liabilities and Equity	5,777,098		5,777,098		5,566,222
Deferred Income Tax Liabilities And Other Liabilities					118,363
Liabilities	5,230,443		5,230,443		5,032,434
Retained earnings	223,260		223,260		211,934
Common stock equity	546,655		546,655		533,788
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes		22,269		46,942
Net income for common stock		41,421		87,348
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
Scenario, Previously Reported | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes		5,372		12,457
Net income for common stock		11,676		26,215
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
Accounting Standards Update 2014-01 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income taxes		1,048		2,096
Net income for common stock		(140)		(280)
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)
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		2,096
Net income for common stock		(140)		(280)
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	46,057	42,660	89,774	83,748
Operating income	19,726	17,956	40,357	40,487
Income taxes	6,875	6,420	14,031	14,553
Net income for common stock	$ 12,851	11,536	$ 26,326	25,935
Bank | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		38,982		76,444
Operating income		17,956		40,488
Bank | Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		43,568		85,564
Operating income		17,048		38,671
Bank | Scenario, Previously Reported | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		39,890		78,260
Operating income		17,048		38,672
Bank | Accounting Standards Update 2014-01 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total expenses		(908)		(1,816)
Operating income		908		1,816
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)		(1,816)
Operating income		$ 908		$ 1,816