Common Stock (Details) - shares		1 Months Ended												12 Months Ended
		Dec. 31, 2015	Nov. 30, 2015	Oct. 31, 2015	Sep. 30, 2015	Aug. 31, 2015	Jul. 31, 2015	Jun. 30, 2015	May. 31, 2015	Apr. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common Stock, Outstanding [Roll Forward]
Shares outstanding, beginning													69,299,559	69,299,559	71,828,208	78,664,029
Issuance related to ESPP														130,622	141,576	217,573
Shares repurchased		0	0	(924,960)	0	(67,436)	(303,807)	(482,586)	(472,000)	(640,000)	(645,000)	(120,000)	(529,100)	(4,184,889)	(3,298,490)	(7,707,014)
Shares outstanding, ending		65,850,386												65,850,386	69,299,559	71,828,208
Shares authorized		800,000,000												800,000,000	800,000,000
Restricted Stock and Restricted Stock Units, Net [Member]
Common Stock, Outstanding [Roll Forward]
Vested restricted stock and restricted stock units, net	[1]													335,518	321,841	340,525
Performance Share Units
Common Stock, Outstanding [Roll Forward]
Issuance of common shares	[1]													269,576	277,164	252,025
SARS
Common Stock, Outstanding [Roll Forward]
Issuance of common shares														0	29,260	61,070
Common Class B
Common Stock, Outstanding [Roll Forward]
Shares authorized		150,001												150,001
Common Class C
Common Stock, Outstanding [Roll Forward]
Shares authorized		400,001												400,001

[1] Vested restricted stock, restricted stock units and performance share units are shown net of shares retired to cover participant tax liability.