Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of the Federal income tax statutory rates to the effective rates [Abstract]
Consolidated tax provision at federal statutory rate (in hundredths)	35.00%	35.00%	35.00%
State income tax provisions, net of federal income tax benefit (in hundredths)	2.40%	4.00%	4.70%
Tax reserve adjustment (in hundredths)	(5.40%)	(4.00%)	(0.30%)
Changes in certain deferred tax balances (in hundredths)	3.10%	(2.70%)	(1.00%)
Noncontrolling interest (in hundredths)	(2.50%)	(1.10%)	(0.40%)
Reversal of tax credits (in hundredths)	0.00%	4.40%	0.00%
Non-deductible transaction costs (in hundredths)	0.00%	0.00%	4.20%
All other, net (in hundredths)	0.40%	0.30%	0.30%
Effective tax rate (in hundredths)	33.00%	35.90%	42.50%
Impact of charge resulting from enactment of Michigan Corporate Income Tax that eliminated certain future tax deductions	$ 10,800,000
Reversal of reserve for uncertain tax positions	12,300,000	9,900,000
Reduction of deferred tax balances based on application of enacted state tax statutes	6,800,000
Reduced deferred tax assets			11,300,000
Income tax charge resulting from health care reform legislation			4,100,000
Deferred income tax liabilities [Abstract]
Property, plant and equipment basis differences	1,959,028,000	1,896,666,000
Intangibles	929,749,000	997,455,000
Other, net	29,564,000	17,584,000
Total	2,918,341,000	2,911,705,000
Deferred income tax assets [Abstract]
Pension liability	306,421,000	246,714,000
Tax operating loss carryforward	154,892,000	294,171,000
Employee benefits	177,464,000	154,711,000
State tax liability	7,422,000	7,358,000
Accrued expenses	43,162,000	27,645,000
Allowance for doubtful accounts	35,181,000	42,733,000
Other, net	14,025,000	22,313,000
Gross deferred income tax asset	738,567,000	795,645,000
Less: Valuation allowance	(78,784,000)	(108,662,000)
Net deferred income tax asset	659,783,000	686,983,000
Net deferred income tax liability	2,258,558,000	2,224,722,000
Deferred tax assets and liabilities are reflected in the following captions on the consolidated balance sheet [Abstract]
Deferred income taxes	2,357,210,000	2,458,018,000
Income taxes and other current assets	(98,652,000)	(233,296,000)
Net deferred income tax liability	2,258,558,000	2,224,722,000
Federal net operating loss carryforward	145,000,000
State tax operating loss carryforward	1,900,000,000
Current [Abstract]
Federal	(3,824,000)	(13,320,000)	18,302,000
State	(1,039,000)	14,252,000	10,260,000
Total current	(4,863,000)	932,000	28,562,000
Deferred [Abstract]
Federal	53,642,000	77,750,000	82,080,000
State	26,859,000	9,661,000	4,357,000
Total deferred	80,501,000	87,411,000	86,437,000
Total income taxes charged to the consolidated statement of operations	75,638,000	88,343,000	114,999,000
Income taxes charged (credited) to shareholders' equity of Frontier [Abstract]
Current benefit arising from stock options exercised and restricted stock	2,937,000	0	0
Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability	(58,551,000)	(97,409,000)	17,501,000
Total income taxes charged (credited) to shareholders' equity of Frontier	(55,614,000)	(97,409,000)	17,501,000
Total income taxes	20,024,000	(9,066,000)	132,500,000
Tax effect of change in method of accounting for repairs and maintenance costs	53,900,000
Gross tax liability for tax positions that may not be sustained under a more likely than not threshold	13,600,000
Additional interest recognized on tax liability	2,100,000
Amount of uncertain tax positions whose statute of limitations are expected to expire during the next twelve months	5,200,000
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits - beginning of year	33,928,000	49,180,000
Gross increases - current year tax positions	3,381,000	8,200,000
Gross decreases - expired statute of limitations	(25,822,000)	(23,452,000)
Unrecognized tax benefits - end of year	11,487,000	33,928,000	49,180,000
Accrued interest on tax liability	$ 2,100,000	$ 3,600,000