Share Repurchase Program (Details) - USD ($)			1 Months Ended	3 Months Ended	9 Months Ended			12 Months Ended
		Aug. 03, 2015	May 31, 2013	Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015	Dec. 31, 2015	[3]	Dec. 31, 2014		Apr. 21, 2016	Feb. 09, 2015	Feb. 06, 2014	Oct. 24, 2012
Equity, Class of Treasury Stock
Stock repurchase program, authorized amount												$ 100,000,000	$ 300,000,000	$ 100,000,000	$ 60,000,000.0
Prepayment of accelerated share repurchase				$ 75,000,000	$ 0		$ 75,000,000
Stock repurchased and retired during period, shares			600,000		2,060,901	[1],[2]		4,907,675	[1]	1,961,085	[1]
Refund of accelerated share repurchase		$ 38,200,000			$ 0		38,179,000
Repurchases of common stock					$ 90,837,000		$ 134,084,000
Stock repurchased and retired during period, average amount per share	[1]				$ 44.08	[2]		$ 43.99		$ 45.29
Stock repurchased and retired during period, value			$ 30,000,000		$ 90,837,000	[1],[2]		$ 215,911,000	[1]	$ 88,815,000	[1]
Accelerated Share Repurchase Agreement [Member]
Equity, Class of Treasury Stock
Stock repurchased and retired during period, shares		800,000
Repurchases of common stock		$ 36,800,000
Stock repurchased and retired during period, average amount per share		$ 46.49

[1] All shares were purchased pursuant to the publicly announced share repurchase program described above. Shares are reported in a period based on the settlement date of the applicable repurchase.

[2] repurchases for the nine months ended September 30, 2016.

[3] The Company entered into an accelerated share repurchase ("ASR") in the second quarter of 2015 under which a prepayment of $75 million was made. Final settlement of the ASR occurred on August 3, 2015, resulting in the delivery to the Company of 0.8 million shares of the Company’s common stock and a return of cash for the remaining amount not settled in shares of $38.2 million. In total, approximately 0.8 million shares of common stock were repurchased under the ASR for $36.8 million, resulting in an average price paid per share of $46.49 under the ASR.