Share-Based Compensation - Compensation Expense and Information on Non-Vested Shares (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
RSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning balance	499
Unvested, Weighted-average grant-date fair value, Beginning balance	$ 32.28
Forfeited, Shares	(21)
Forfeited, Weighted-average grant-date fair value	$ 32.63
Vested, Shares	(128)
Vested, Weighted-average grant-date fair value	$ 32.74
Granted, Shares	257
Granted, Weighted-average grant-date fair value	$ 34.19
Unvested, Shares, Ending balance	607
Unvested, Weighted-average grant-date fair value, Ending balance	$ 32.98
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning balance	542	[1]
Unvested, Weighted-average grant-date fair value, Beginning balance	$ 37.10
Forfeited, Shares	(159)
Forfeited, Weighted-average grant-date fair value	$ 39.77
Granted, Shares	723
Granted, Weighted-average grant-date fair value	$ 36.76
Unvested, Shares, Ending balance	1,106	[1]
Unvested, Weighted-average grant-date fair value, Ending balance	$ 36.50
Deferred Compensation, Share-based Payments [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Ending balance	30
Unvested, Weighted-average grant-date fair value, Ending balance	$ 29.73
Vested, Shares, Ending Balance	116
Vested, Weighted-average grant-date fair value, Ending balance	$ 34.88
Outstanding, Shares, End Balance	146
Outstanding, Weighted-average grant-date fair value, Ending balance	$ 33.81
January 2014 [Member] | Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares	432
Granted, Weighted-average grant-date fair value	$ 32.97

[1] Non-vested performance shares are based on a maximum potential payout. Actual shares granted at the end of the performance period may be less than the maximum potential payout level depending on achievement of performance share objectives. During the first quarter of 2014, the Company granted maximum performance shares of 432 thousand based on certain annual management objectives, as determined by the Board of Directors. These performance shares vest proportionately over a three-year period and have a grant-date fair value of $32.97.