Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended					6 Months Ended		9 Months Ended	12 Months Ended
		Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings per share — Basic:
Earnings from continuing operations		$ 85,917	$ 53,326	$ 83,895	$ 75,721	$ 49,126	$ 139,243	$ 124,847	$ 208,742	$ 220,225	$ 243,275	$ 200,668
Less: Distributed and undistributed earnings allocated to nonvested stock		(246)			(302)		(393)	(582)
Earnings from continuing operations available to common shareholders — Basic		$ 85,671			$ 75,419		$ 138,850	$ 124,265
Weighted average common shares outstanding - Basic (shares)		52,827			52,564		52,712	52,612
Earnings from continuing operations per common share — Basic	[1]	$ 1.62			$ 1.43		$ 2.63	$ 2.36
Earnings per share — Diluted:
Earnings from continuing operations		$ 85,917	$ 53,326	$ 83,895	$ 75,721	$ 49,126	$ 139,243	$ 124,847	$ 208,742	$ 220,225	$ 243,275	$ 200,668
Less: Distributed and undistributed earnings allocated to nonvested stock		(244)			(299)		(390)	(578)
Earnings from continuing operations available to common shareholders — Diluted		$ 85,673			$ 75,422		$ 138,853	$ 124,269
Weighted average common shares outstanding - Basic (shares)		52,827			52,564		52,712	52,612
Effect of dilutive equity awards (shares)		468			482		492	472
Weighted average common shares outstanding — Diluted (shares)		53,295			53,046		53,204	53,084
Earnings from continuing operations per common share — Diluted	[1]	$ 1.61			$ 1.42		$ 2.61	$ 2.34
Anti-dilutive equity awards not included above (shares)		363			412		273	314

[1] EPS amounts may not be additive due to rounding.