Net Income Per Common Share (Calculation Of Net Income Per Common Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income Per Common Share [Abstract]
Net income (loss) attributable to common shareholders of Frontier	$ 67,755	$ 35,400	$ (38,460)	$ 48,140	$ 24,879	$ 67,000	$ 17,989	$ 26,768	$ 112,835	$ 136,636	$ 149,614
Less: Dividends paid on unvested restricted stock awards									(2,531)	(2,901)	(3,743)
Total basic and diluted net income attributable to common shareholders of Frontier									$ 110,304	$ 133,735	$ 145,871
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)									999,126	997,665	994,753
Less: Weighted average unvested restricted stock awards (in shares)									(6,467)	(7,128)	(4,901)
Total weighted average shares outstanding - basic (in shares)									992,659	990,537	989,852
Net income per share attributable to common shareholders of Frontier (in dollars per share)	$ 0.07	$ 0.04	$ (0.04)	$ 0.05	$ 0.02	$ 0.07	$ 0.02	$ 0.03	$ 0.11	$ 0.14	$ 0.15
Effect of dilutive shares (in shares)									1,338	1,263	1,415
Effect of dilutive stock units (in shares)											557
Total weighted average shares outstanding - diluted (in shares)									993,997	991,800	991,824
Diluted net income per common share attributable to common shareholders of Frontier									$ 0.11	$ 0.13	$ 0.15