Employee Benefits and Stock-Based Compensation - Outperform Stock Options (Details) - Outperform Stock Options - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Options outstanding, beginning (in shares)	614,980.00000	1,217,869.000000	2,148,865
Options granted (in shares)	0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	(6,875)	(12,945)	(52,901)
Options expired (in shares)	0	0	(106,844)
Options exercised (in shares)	(608,105)	(589,944)	(771,251)
Options outstanding, ending (in shares)	0	614,980.00000	1,217,869.000000	2,148,865
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures
Options, Beginning, Initial Strike Price Per Unit, Minimum (in dollars per share)	$ 20.29	$ 16.99	$ 14.1
Options, Beginning, Initial Strike Price Per Unit, Maximum (in dollars per share)	26.69	27.53	36.60
Options, Beginning, Weighted Average Initial Strike Price (in dollars per share)	$ 22.77	$ 22.76	$ 23.99
Options, Beginning, Aggregate Intrinsic Value		$ 48,500,000	$ 88,040,000.00	$ 31,600,000
OSO units Outstanding, Average Remaining Contractual Term		4 months 13 days	10 months 24 days	1 year 5 months 15 days
Options granted, Initial Strike Price Per Unit, Minimum (in dollars per share)	$ 0	$ 0	$ 0
Options granted, Initial Strike Price Per Unit, Maximum (in dollars per share)	0	0	0
Options granted, Weighted Average Initial Strike Price (in dollars per share)	0.00	0.00	0.00
Options forfeited, Initial Strike Price Per Unit, Minimum (in dollars per share)	20.29	20.29	16.99
Options forfeited, Initial Strike Price Per Unit, Maximum (in dollars per share)	26.69	26.69	27.53
Options forfeited, Weighted Average Initial Strike Price (in dollars per share)	26.03	22.81	22.99
Options expired, Initial Strke Price Per Unit, Minimum (in dollars per share)	0	0	36.6
Options expired, Initial Strke Price Per Unit, Maximum (in dollars per share)	0	0	36.6
Options expired, Weighted Average Initial Strike Price (in dollars per share)	0.00	0.00	36.60
Options exercised, Initial Strike Price Per Unit, Minimum (in dollars per share)	20.29	22.15	14.7
Options exercised, Initial Strike Price Per Unit, Maximum (in dollars per share)	26.69	22.97	27.53
Options exercised, Weighted Average Initial Strike Price (in dollars per share)	22.73	22.32	24.26
Options, Ending, Initial Strike Price Per Unit, Minimum (in dollars per share)		20.29	16.99	$ 14.1
Options, Ending, Initial Strike Price Per Unit, Maximum (in dollars per share)		26.69	27.53	36.60
Options, Ending, Weighted Average Initial Strike Price (in dollars per share)		$ 22.77	$ 22.76	$ 23.99
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 14,000,000	$ 13,000,000	$ 19,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	992,446	622,755	1,000,000
On or After April 1, 2007
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Life of Award	3
Percent vested after three years	100.00%
Performance Range 1
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Performance Qualifier to Index, Maximum	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Success Multiplier of Pre Multiplier Gain	0.00
Performance Range 2
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Performance Qualifier to Index, Minimum	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Performance Qualifier to Index, Maximum	11.00%
Share-based Compensation Arrangement by Share-based Payment Award, Success Multiplier of Pre Multiplier Gain	0.36
Performance Range 3
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Performance Qualifier to Index, Minimum	11.00%
Share-based Compensation Arrangement by Share-based Payment Award, Success Multiplier of Pre Multiplier Gain	4.00