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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Income Per Common Share [Abstract]
Net income attributable to common shareholders of Frontier	$ 13,946	$ 41,993	$ 37,680	$ 39,274	$ 67,755	$ 35,400	$ (38,460)	$ 48,140	$ 132,893	$ 112,835	$ 136,636
Less: Dividends paid on unvested restricted stock awards									(3,043)	(2,531)	(2,901)
Total basic and diluted net income attributable to common shareholders of Frontier									$ 129,850	$ 110,304	$ 133,735
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)									1,001,812	999,126	997,665
Less: Weighted average unvested restricted stock awards (in shares)									(7,394)	(6,467)	(7,128)
Total weighted average shares outstanding - basic (in shares)									994,418	992,659	990,537
Basic net income per common share attributable to common shareholders of Frontier	$ 0.01	$ 0.04	$ 0.04	$ 0.04	$ 0.07	$ 0.04	$ (0.04)	$ 0.05	$ 0.13	$ 0.11	$ 0.14
Effect of dilutive shares (in shares)									3,744	1,338	1,263
Total weighted average shares outstanding - diluted (in shares)									998,162	993,997	991,800
Diluted net income per common share attributable to common shareholders of Frontier									$ 0.13	$ 0.11	$ 0.13