Stockholders' Equity - Narrative (Details) - USD ($)			3 Months Ended				6 Months Ended
	Jul. 28, 2016	May 16, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Oct. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Payments of dividends							$ 34,029,000	$ 33,271,000
Dividends declared per common share (USD per share)		$ 0.92	$ 0.92	$ 0.92	$ 0.92	$ 0.875	$ 1.84	$ 1.75
Dividends payable			$ 16,792,000		$ 17,082,000		$ 16,792,000
Treasury stock reissued (shares)							112,176
Treasury stock reissued							$ 4,000,000
October 2014 Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount									$ 150,000,000
Stock repurchased during period, shares							395,891
Stock repurchased during period, value							$ 35,000,000
Cumulative amount of shares repurchased (shares)			600,378				600,378
Cumulative payments for repurchase of common stock			$ 52,500,000				$ 52,500,000
Remaining authorized stock repurchases			$ 97,500,000				$ 97,500,000
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Dividends declared per common share (USD per share)	$ 0.92